A telescope is an instrument that is used to view distant objects. If you want to look at the planets, you can use a telescope. The higher the magnification on the telescope, the better your view will be.
Galileo is often credited with the invention of the telescope, but this is incorrect. Although he didn't invent it, he did improve it — a lot. He didn't name the telescope either; Greek mathematician Giovanni Demisiani did, in 1611. Telescope is from the Greek roots tele."far," and skopos, "seeing;" so it literally describes what the instrument does. As a verb, telescope means "to become smaller through one part sliding into another," the way a portable collapsing telescope does.