Stellarium is a visualization of the night sky at the given time and location, including planets, Moon and stars.
The sky view also depends on geographic location and time of the year. The provided applet allows to experiment with various locations, dates and times. It contains 518 brightest stars from the Yale Bright Star Catalog. The number of visible stars in the sky depends on observing conditions; even simple telescope can see much more of them than a naked eye. More stars can be seen outside the big cities and especially in the mountains.
Planets have more complex path through the sky, as they also follow they path around the Sun. During the single night, the influence of this planet own movement is small and a planet moves very much like a star. However during multiple days the planets own movement changes its visible position in relate to the real stars and other planets. The word planet means a roaming star or wandering star. There are also planets outside Solar system but these are tricky to see even with the most advanced tools.
Not all planets are visible with the naked (use checkbox on the applet to turn on "invisible" planets on).
The night sky studies were and stay important in various cultures. As the sky view depends on location, time of the year and time of the night, it can be used to determine all three of them. Many cultures have drawn constellations between stars in the sky, mentioning them in legends and mythology about their deities.
The impressive night sky applet by Benjamin Crowell, from the Planet finder project.