A thesaurus lists words. This explains the difference between them: who is helping, how much, how urgently, and how formal the sentence needs to be.
Every word comes with one sentence on when to use it and one on when not to.
Each entry shows the word in a real sentence, so you hear the register before you use it.
Drop in the line you are stuck on and see which word for help fits it, and why.
English has a dozen words for help, and almost none of them mean the same thing.
The idea behind the name