Can someone explain in simple terms Cassandra nodetool commands like compact and cleanup?

**Hello Everyone** I am new in databases and i am trying to understand some Cassandra commands. I would like to know about the following commands : - nodetool compact - nodetool cleanup - nodetool repair - nodetool garbagecollect I would appreciate some simple and clear answers like -> nodetool help : it shows all the commands and their usage. >The problem i am trying to solve is that after i delete (a lot of data) the storage is still full. I change the gc_grace_seconds to 1 day and still nothing. So if i need to clear the space manualy right now which commands should i run and in what order? *Thanks for your time*