What items on Earth are used to look into space?

Strictly speaking, you cannot see "outer space", because space is almost entirely empty.

That means that there is nothing there to reflect light back to our eyes, so we don't

see anything.

But to view things on the other side of the "almost entirely empty" outer space -

things like moons, planets and stars - we typically use many versions of telescopes,

although you can see examples of each with your bare eyes.