A kundli, also called a janam kundli, janam patri or birth chart, is a picture of the sky at the moment and place you were born. It shows where the nine Vedic planets stood against the twelve zodiac signs, and that snapshot is what Vedic astrology (Jyotish) reads.
The three things to look at first
Lagna (ascendant). This is the sign rising on the eastern horizon when you were born. It fixes the first house and, with it, the layout of the other eleven. It changes roughly every two hours, which is why birth time matters so much.
Rashi (Moon sign). The sign the Moon was in. It describes your mind, feelings and habits, and it is the sign Vedic daily horoscopes are written for.
Nakshatra (birth star). The Moon's position is also divided into 27 stars of 13 degrees 20 minutes. Your nakshatra sets the planet your dasha cycle begins with, and is used in naming and in kundli matching.
The twelve houses
Each house governs an area of life. The 1st is you and your body, the 2nd family and money, the 3rd courage and siblings, the 4th home and mother, the 5th children and creativity, the 6th work and health challenges, the 7th partnership and marriage, the 8th change and the unseen, the 9th fortune and father, the 10th career, the 11th gains and friends and the 12th rest, loss and foreign lands.
The planets sitting in a house, and the planet that rules the sign on that house (its lord), colour that area of life.
The nine planets (grahas)
The Sun, Moon, Mars, Mercury, Jupiter, Venus and Saturn are joined by two shadow points, Rahu and Ketu, where the Moon's path crosses the Sun's. Each planet has a nature: Jupiter expands and guides, Saturn tests and builds, Mars drives, Venus attracts and harmonises, Mercury thinks and trades, Rahu amplifies and Ketu detaches.
North Indian and South Indian charts
The same chart can be drawn two ways. In the North Indian diamond, the houses are fixed in place and the signs move around. In the South Indian square, the signs are fixed and the lagna is marked. Pick the style you grew up with; the information is identical.
Dasha: the timeline of your chart
A kundli is not only a map but also a timeline. In the Vimshottari system, a 120-year cycle is divided among the nine planets, and each planet's period (mahadasha) brings its themes to the front. Which period you are in now is often the most useful single fact in the chart.
A fair word of caution
A kundli describes tendencies and timing, not a fixed fate. Read it as a mirror for reflection. For anything involving health, money or law, speak to a qualified professional first.