what is a claim?
In essence, a "claim" is a square region of land that is marked in your name on the server, which, by default, other players cannot build, break or pillage within. The Spot uses a plugin called GriefPrevention to do this. Claims have some other properties, too. Creeper and Wither explosions, Endermen block moving and TNT will not work by default within claims and even fluids such as water and lava cannot flow from outside to inside a claim.
Claims work on a system of "Claim Blocks", of which you passively earn 200 of every hour (obtainable from crates too) Each square block in a claim you make uses one of your claim blocks. This means that claims can only be of finite size. In-game, claims are visualized by temporary markings of gold and glowstone that are only temporary and cannot be mined.