ArchitectMC
Your first claim
A claim is a 16×16 chunk that only you (and people you trust) can build in. Stand where you want the house, then type /claim. /claims opens the same thing in a chest menu.
The two-chunk gap
You cannot claim right next to someone else’s land. Keep two empty chunks between you and a stranger. Your own claims can touch each other.
How many chunks
New players start with a small limit. Rank up by playing and you can claim more. Voting on all four sites in one day adds +1 claim chunk on top of that rank limit — it stays. Type /claimbalance to see used, remaining, and vote bonus. If the server says you are at your limit, check that command before assuming it is a bug.
Friends
Stand in the chunk and use /trust <name>. That person can build and use things on that chunk only. /untrust takes it back.
/trust region <player> covers every connected chunk of the claim you are standing in. A second base that does not touch this one is left alone. /trust region <team> trusts that team at recruit and above on the same region. /untrust region removes it.
Visitor flags
Stand in a chunk you own and type /claimflags. Only you can change them. The menu is three rows. Visitors lets other people use doors, buttons and chests — it never lets them break or place. Building is who can break and place. Protection is explosions, liquids, fire and pistons. Green on the first two means anyone. Green on Protection means that thing is blocked. Defaults stay locked. The menu changes this chunk only. Chest shop signs still work when chests stay locked. Full list: wiki.
Let someone claim next door
/neighbour <name> is spacing only. They can take a reserved plot in this chunk’s two-chunk gap. It does not let them build on your land — that is still /trust.
Hand a plot to someone else
Stand in a chunk you own and type /claim transfer <name>. They must accept, and they need a free claim slot. After the transfer you two can sit next to each other on that plot; strangers still need the two-chunk gap.
Leaving
/unclaim drops the chunk you are standing in. Do not unclaim a shop you still want.