title says all, it means that it doesnt necesarily have to be done in one sitting or something else?

A multi-segment run is one where the runner saves the game and/or loads from a save (excluding New Game+ start saves, which say "Operation Snake Eater completed" on them). The primary purpose of multi-segment runs is allowing the runner to do strats that are generally considered too unsafe for a single-segment run, since the runner has as many attempts at the short segment as they like.

Multi-segment runs also allow the runner to do strats that are otherwise impossible, most notably, killing The End by old age, which is by far the fastest way to kill him. However, this is only possible in multi-segment, as it requires the runner to load from a save. Other, less significant, time saves are doing caution strats on European Extreme, then using a save to clear that caution in the next room.

Multi-segment runs can be done in as many sittings as you please, you can take as long as you like to do them, and you can use as many saves as you like.

thanks !!! i think that i will try one of these, at least in my first tries, then i will go for full runs.