'Houses', 'Bhavas', 'Sthanas'.

The Birth Chart used in the Hindu Vedic Astrology is shown as above. This is the most common way of depicting the Kundali especially in the Northern India.
In Southern India the Chart is depicted in a Square format. However I will be using the above mentioned Chart Format.

In any Chart/ Kundali there are 12 compartments which are called 'Houses', 'Bhav', 'Sthan'. The topmost house is counted as the first house. (Number 1 House in the figure.) Then subsequently all the other houses are counted in anti-clockwise direction.

Planets, 'Grahas'

There are total 12 planets, 'grahas' considered in astrology.
Ancient Vedic Astrology only 9 planets are considered. The recently discovered 3 planets namely Uranus ('Harshal'), Neptune and Pluto were obviously not considered.
However it is wise to consider all 12 planets. 

The 12 Planets are as follows.

They are revolving around the Sun in their respective orbits. Exception is the Moon, Rahu, Ketu. As you are all aware that the Moon is a satellite of our Earth. Moon is revolving around the Earth and Earth in turn is revolving around the Sun in its orbit.
Rahu and Ketu are not the actual planets at all. They are actually only intersection points of the Earth and the Moon. However since these cosmic points have considerable influence on the nature they are considered as planets in the astrology.

Signs, Rashis

There are twelve 12 Signs, Rashis as follows.

The Signs or Rashis are imaginary divisions of the Zodiac. 360 degrees of a full circle are divided in 12 equal parts, each of 30 degrees, called a Rashi or Sign.
As the Earth is revolving around its own axis and takes 24 hours for that, we see the Signs, Rashis revolving around us.

Ascendant or the Lagna
The Sign, Rashi rising at the Eastern horizon at the time of the birth is the Ascendant or the Lagna. As you must have gathered that at about every 2 hours (Division : 24 hours/12 signs) a new sign is going to rise, and hence the ascendant or the lagna the starting point of the chart is going to change. Same way every 4 minutes the Ascendant or the Lagna degree is going to change.
The subsequent Signs, Rashis are written in the next - next houses in the anti-clockwise direction.

Fully Plotted Birth Chart, Janma-Kundali

Lastly all the precise positions of all the 12 planets at the time of the birth are plotted in the chart.
Hence the Birth Chart or the Janma Kundali is the diagrammatic representation of all the planets at the precise moment of time of the birth.
Easy Example : Suppose the birth was at about 7:00 A.M. i.e. just after the sunrise. That means the Sun will be plotted in the first house (Eastern Horizon). Further imagine that, the day was Full Moon Day i.e. Sun and Moon are 180 degrees from each other. That means the Moon will be in the 7th house.

Now finally lets have a look at the following complete birth chart, Janma Kundali where all the planets and the signs are plotted.

As you can see that at the time of the birth Leo, Sinha Sign, Rashi was arising at the eastern horizon and the birth time must have been near about the sunrise as the Sun is in the first house.
A rough idea can be brought out about the time of the birth by looking at the Sun's position in any chart.

I hope you must have got a fair idea about the Birth Chart or the Janma-Kundali layout