What does it mean to win "by force"? I occasionally see annotations/commentary where a move / line is said to make (for example) white win "by force". I am unsure if it has the general sense of "this move initiates a forcing sequence where white will come out on top" or something more specific, say, "with this move, white exerts indefensible pressure ('force') on a particular square / sector (say more attackers than defenders on f7 with further defense impossible) that will give them victory."

What exactly does it mean?
"Wins by force" means that the move leads to a series of moves that makes it impossible for the losing side to defend the position. Here, the definition of "winning" can vary between annotators. Checkmate is the extreme case of winning. Having an advantage of two pawns without any compensation for the opponent is somewhere at the low end of a winning position. The whole term "by force" refers to the fact that the opponent is unable to avoid getting a worse / losing position. At what point does a position become winning? That can depend on the position and the players involved. Usually, higher rated players have higher expectations on them to win better positions. If a game is annotated as "this move wins by force" then it means that the annotators expects the player at the board to win the position that arises after the sequence of moves is completed.