The picture shows the typical layout of the sections of a modern symphony orchestra. The violins are on the left, the cellos and basses are on the right. The brass is at the back, and the woodwind just in front of the brass.
If you left click on any section, you will hear a melodic fragment played on the instrument in that section, and you will see a picture of your chosen instrument. If you have stereo speakers in your set-up, you should hear violins coming from the left, and double basses from the right, and so on. If you right click, you will be taken to a screen with detailed information about your chosen instrument, as well as a list of music pieces in the Musical Discovery database which feature the chosen instrument, and clicking on any item in that list will cause the music to be played.
If you click the green button at the foot of the screen "Listen to each instrument in turn", the program will show a picture and play a sample for each orchestral section. Whilst this is happening, the button will turn red, and its caption will change to "Stop Listening", so you can click it again at any time to stop the demonstration.