But if lag is always there online, how can GGPO “get rid of lag?”
It can’t actually “get rid of lag,” but it can allow the game to proceed as if there wasn’t any. With GGPO, in our example above Alex can choose how many frames the game delays his input on his own console, meaning he can choose to have the game react instantly. Thus, for his own character he experiences zero input lag. This means all his combos, links, throw techs and other timing-sensitive things will feel exactly the same as if Alex were playing offline, making his experience infinitely more useful.
So it all depends on what you want out of the game – GGPO allows users to choose to experience anything between zero and eight frames of input lag. Those who want the true tournament experience can choose zero lag and get training that will apply equally well offline, but they will have to get used to dealing with rollbacks. Alternatively, players who want smoother visuals but can tolerate a bit of input lag can choose 2 to 4 frames of lag, which is generally acceptable for most people and will have fewer visual oddities on average connections. And casual players can choose 5 to 8 frames of lag, which means the game will look super smooth but gameplay will lag quite a bit.