to help: to come to someone's aid by adding your strength to theirs
At its core this word is about lending your strength to someone who is up against more than they can handle alone. It is not advice or sympathy from a distance; it is stepping in and acting on the person's behalf, usually when they are outmatched, in danger, or too weak to manage by themselves.
The same act looks different depending on who does it. Armies and allies use the word for coming to one another's aid in battle, marching out to reinforce a side that would otherwise lose. The poor, the orphan, and the cornered cry out for someone to help them when no one else will. And again and again, especially in the Psalms and Isaiah, it is God who helps: stepping in to rescue his people when their own strength has run out. These are not different meanings of the word but the same meaning in different hands, so the senses below sort the occurrences by who is doing the helping rather than by any shift in what the word itself means.
Because the help is concrete action and not mere goodwill, the word often carries the sense of help that actually decides the outcome. To say the LORD helped Israel is to say he turned the situation, not that he wished them well.