The Ascendant is the point where local space intersects the ecliptic on the eastern horizon. The Earth rotates on its own axis once a day, i.e. if we look east or west on the horizon line from where we are on Earth and do nothing else all day and all night but focus on this one point, then all the constellations of the ecliptic will pass our eyes once and we will have rotated 360° in a circle once due to the Earth's rotation. That point in this 360° circle that is just rising on the eastern horizon is called the Ascendant (the astrological 1st house), and the point that is setting opposite on the western horizon at the same time is called the Descendant (the astrological 7th house).
When a human being is born, the point on the eastern horizon that is rising at this time of birth (seen from the place of birth, as determined by geographic coordinates) is the so-called ascendant of this individual. There will always be one point in this 360° band that we can see circling around us on the eastern horizon (and around other parts of the sky) due to the earth's own rotation, that is rising on the eastern horizon at this very moment, and this specific point is the Ascendant of the newborn.
In astrology, we divide this 360° circle of the ecliptic into 12 equally sized sections. Each of these sections comprises 30° of this celestial space, so that each point of this 360° celestial space is covered by a 30° section.
We call these 30° sections astrological signs of the zodiac, and each of these signs of the zodiac such as Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius and Pisces will rise on the eastern horizon once a day for about 2 hours. Since there are 12 astrological signs of the zodiac, each with a celestial space of 30°, and the earth rotates once around its own axis in about 24 hours (more precisely in 23h 56min), each sign of the zodiac comprises the part of the sky that rises on the eastern horizon for about 2 hours a day.
Depending on into which of these 30°-sections the eastern point on the horizon falls at the time of a person's birth, the section where this point falls becomes the ascendant of the newborn.
Since the zodiac sign of the ascendant therefore changes 12 times every day, this also means that people are born every day (at different times and at different places) with the point on the eastern horizon as at the place of birth being different 30° sections of celestial space. So, in sum, therefore, every day people are born with all 12 ascendants.
This shows that people are much more individual than their sun sign that we generally identify ourselves with when we are asked about our zodiac sign. Are we really only to look at the position of the sun as the main factor, as we are used to in newspaper horoscopes? After all, the position of the Sun as seen from the Earth changes very slowly and stays in one sign for a whole month!
The ascendant, on the other hand, is much more individual, changing approximately every 2 hours. The Sun sign (which we commonly associate with) and the ascendant sign are therefore two different phenomena, and we are advised to begin our astrological analysis primarily from the ascendant.
The ascendant of a person is so very important because it symbolizes the body and the life path of a person. The body is that which man carries into this world and where he comes from. The life path is the direction that man will be influenced to go. Like when I'm driving a car at 100 km/h on the road: I may be able to slowly change the direction I'm moving in if I move the steering wheel around or if I turn and thereby head for a different destination. But can I really change the direction of my life's journey completely by 180°?
The path of life and the course of action of a human being can be understood by where the planet, which rules over the zodiac sign of the person's ascendant, has "gone". In other words, we look at where this planet (= the ascendent lord) is located at the time of birth (relative to the ascendant) in the celestial space of this 360° band.
Each zodiac sign is " ruled " by a planet. This means that each planet takes care of a certain section of this 360° celestial space in the form of the zodiac signs and is in charge that this section of the sky is doing well. As for the Sun, its section of the sky is zodiac sign called Leo; for the Moon, it is the section of the sky called Cancer; for Mars, the sections are called Aries and Scorpio; for Mercury, the sections are aclled Gemini and Virgo; for Jupiter, these are Sagittarius and Pisces; for Venus, these are Libra and Taurus; and for Saturn, Capricorn and Aquarius.
The point in the sky where the planet ruling the ascendant is located relative to the ascendant at the time of birth (in which sign, house, ...), that location relative to the point of the ascendant will be the direction that the newborn person will be influenced to go.
That is why the ascendant is very, very important astrologically. The first thing I look at in the horoscope is: what is the Ascendant and where is the ascendent lord situated. In what environment and in what position relative to the ascendant does the ascendant lord reside? That alone is very revealing.
Once the point of the ascendant has been determined, all other important points on this 360° circle (the so-called astrological houses) are also determined. Each of these 12 astrological houses stands for one area of life. Just by knowing the ascendant, so much can be said about the qualities of these 12 areas of life. The individual astrological houses are always arranged one after the other on this 360° band of the zodiac signs: the 1st house is always followed by the 2nd house, then the 3rd house follows, then the 4th house and so on.
For example, for Leo ascendants it is essentially already a given that the quality of the 2nd house will have characteristics of the zodiac sign Virgo and thus also characteristics of Mercury, who " takes care " of the zodiac sign Virgo (which is part of what makes a Leo ascendant a Leo ascendant). Of course this by no means says everything about the individual, because every horoscope has to be read individually, but quite a lot can already be derived just by knowing the ascendant.
For Cancer Ascendants, on the other hand, the quality of the 2nd house has more characteristics of the zodiac sign of Leo (which is the zodiac sign that comes directly after Cancer, and is therefore the second zodiac sign for Cancer ascendants) and therefore also of the Sun, who "takes care " of the zodiac sign of Leo.
In this way, a great deal can be said about the houses of each of the 12 Ascendants.
What makes an Ascendant to what it is in its prototype is basically exactly this relation of the signs of the Zodiac and the planets ruling over them ( together with the astrological areas of life/houses falling within them ) in relation to this ascendant. What these look like in detail is revealed by studying the planets of an ascendant.