There are multiple command permission levels (operator permission levels). This was introduced in Minecraft 1.7.10 to allow users more control over what players can run and what not - especially on servers. The lowest true level is 1, the highest is 4. Higher-level inherits all the permissions from the lower levels.
Permission level list
|No level||Commands allowed in a world with cheats disabled|
|1||No commands can be executed|
Commands /clear, /difficulty, /effect, /gamemode, /gamerule, /give, /summon, /setblock, /tp
|3||Commands /ban, /deop, /kick, /op can be used|
|4||Command /stop to stop the server can be used|