1. She used to help him with his homework.
2. What can you help him with?
3. I want to help him with something.
4. I want to help him with that.
4-1. I want to help him tie the ribbon.
4-2. I want to help him to tie the ribbon.
(Does 'with' mean about? Can we substitute 'about' or 'concerning' for 'with'? The last 3 sentences are the same, right? )
No, "about" and "concerning" do not mean exactly the same thing in the context here. "With" is the best preposition.
And, no, the last three do not all mean the same thing. 4. does not specify what you want to help him do. 4-1 and 4-2 do specify (tie the ribbon). In 4-2, "to tie" is incorrect, or, at best clumsy and redundant. 4-1 is best.
In sentence 1, "She used to help him with his homework," the phrase "with his homework" describes what kind of help she used to give him.
In sentence 2, "What can you help him with?" the word "with" is used to ask what specific things you can assist him with.
In sentence 3, "I want to help him with something," the word "with" is used to indicate that you want to assist him in a particular matter, but it doesn't specify what that thing is.
In sentence 4, "I want to help him with that," the word "with" refers to helping him in relation to a specific thing. The word "that" is used to refer back to something mentioned previously, indicating that the speaker wants to help with a specific matter that has been discussed.
Regarding sentences 4-1 and 4-2, they are indeed the same in meaning. Both sentences convey the idea that the speaker wants to assist him in tying the ribbon. The phrase "help him tie the ribbon" is a more colloquial way of expressing the same meaning as "help him to tie the ribbon."
In these sentences, the word "with" doesn't mean "about" or "concerning." Instead, it indicates the specific area or task in which the speaker wants to offer assistance. You cannot directly substitute "about" or "concerning" for "with" in these sentences without changing the meaning.