These are the classical planets: the ones people have been observing since the first person looked up in the night sky. The word planet literally means "wanderer" in Greek, and it refers to how these celestial bodies appear to move through the stars.
Mercury, Venus Mars Saturn and Jupiter are some of the brightest objects in the sky. Depending on the time of year, you might have to get up pretty early in the morning to see some of these objects, but it's always a good way to start the day. Pay special attention to how Venus looks: it shows a phase and is one way to prove (as Galileo did) that it moves around the Sun and not the Earth.