The inner planets are;- Mercury, Venus, Earth and Mars. Earth is the only planet which has atmosphere, water on the surface or know of to have water(Mars might have water underground), and life.
Mercury is pretty much a small planet on fire by day, but freezes at night.
Venus is a gas planet which is usually on fire in places too, but has mass ice craters on the surface.
Earth, well just look out your window.
Mars may have been an earth like planet at one stage, (still unknown) but is known as the red planet due to its volcanic activity. Mars also has the biggest mountain/volcano on any known planet called Mt Olympus. It's 3 times the size of Mt Everest.
Hope this helps!! :)