The birth chart is the still snap of zodiac at the time of his/her birth. The planets placed in different signs get arranged in the birth chart as per the birth ascendant.
Ascendant/Rising Sign in Indian Astrology :
As explained above, the ecliptic passes through the middle of the zodiac belt that extends to nine degrees on its each i.e. north or south side. All the planets remain within the limits of the zodiac. The earth rotates around its axis once in twenty four hours from west to the east. Consequently all the planets appear to be revolving around the earth from east to west. The zodiac along with all the planets and signs fixed upon it also appears to be revolving around the earth from east to west. This indicates that all points on the signs and planets on the zodiac will appear to successfully rise in the eastern horizon and set at the western horizon once in 24 hours. Thus, for every point and time on earth there would be a unique point on a particular zodiac sign which will be rising at the eastern horizon.
At the time of birth of a person the point in the particular zodiac sign, expressed in terms of longitude, which is rising in the eastern horizon is known as the Ascendant (Lagna) or the Rising Sign of the person.
Janma Rashi/Moon Sign/Moon Ascendant in Indian Astrology :
The house in which Moon is placed in the birth chart of a person is known as the Moon sign. For example the placement of Moon in the sign Taurus in a birth chart indicates that the Moon sign/Janma Rashi of the person concerned is Taurus.
What is Sun Sign/Sun Ascendant in Indian Astrology :
Just like the Moon sign, the location of the house in which Sun is placed in a birth chart is known as its Sun sign. Western astrology gives great importance to the Sun signs. This has been observed that the Sun sign of a person on the basis of Western astrology and Vedic Astrology vary by one sign. The reason being according to the Western astrology the zodiac is moving, whereas, according to the concepts of Vedic astrology the zodiac is fixed.
Relevance of Indian Astrology by Indian Astrologer :
According to the Vedic philosophy, what would happen to a person in this life is predetermined and a lot depends on the deeds i.e. Karma of our past lives. The relevance of 'free will' is a matter of debate. However we being astrologers believe that almost 70 percent of what would happen to us may be predicted by blending various principles of Vedic astrology. However the remaining thirty percent is the critical factor and created by our present deeds and may be controlled by taking rational decisions and putting in efforts in the appropriate direction as per demand of the situation. Here this is important to mention that Vedic Astrology is the only science that provides us the guidance to improve this critical factor comprising of the thirty percent.
This is the hard fact that nobody of this earth can stop the rain from falling. However, this depends on you, whether you wish to carry and utilize an umbrella to protect yourself from the falling water or not.