Renting and buying are two ways of achieving the same thing: having a property in which you can live.
Renting
When you rent, you don't own the property. You lease it as you would a car. For the duration of the lease, you can live in the property and use it within certain conditions set down by the tenancy agreement.
Buying
When you own a property, it's yours. You can do what you like with it provided you abide by local ordinances. You can lease it out, live in it, or fix it up to sell later on.
Differences
Financially, renting is a smaller commitment. It's easy to pack up and move elsewhere if you choose to and general maintenance issues will fall to your landlord to deal with.
Compared to buying a house, it's much less hassle and is quick to finalize.
However, owning a house opens up more options and gives you something you can keep for the rest of your life, if you choose to.