In minecraft, especially in multi-player survival servers, you will need a home to protect yourself, for a beginner, you might build an temporarily above-ground house, but later, you will need to eventually build a base to keep yourself (or your friends) safe from monster and/or other players.

Sky Base

the good thing about a sky base is that it has a high ground advantage, it means that you can see your enemies approaching you before they attack and you can have a good view of the land around you base.

Under-Ground base

Under-Water base

Half-submerged bases

Nether Bases

End Bases