>>7323296Saber is just the Servant moniker (e.g. Lancer, Archer, Assassin etc.), but the name "Saber" is most associated with the one from the first Fate entry (Fate/Stay Night), who is essentially a female King Arthur.
With this in mind some of those Sabers are just alternate versions of the same character (OG Saber being the main one, Saber Alter being her corrupted version in-story from Heavens Feel, Saber Lily being alternate younger version etc.). Other Sabers that resemble the OG Saber are mainly aping her design due to her popularity even though they're meant to be different characters altogether (Nero Saber, Sakura/Okita Saber). Mordred is kind of a special case though, because even before all the Saber clones, she really was written to be the bastard offspring clone of the OG Saber in-universe and being a literal cloned homunculus is actually part of her story.
That said, among those are other versions of the OG Saber, which basically amount to more what-ifs (older, younger versions, that lived different lives etc.),or gimmicky fanservice versions (maid, bikini outfits). The thing is though, with Type-Moon often playing up the idea of parallel universes, they can easily shove all of them together for the sake of crossover stories not unlike Batman or Spider-Man.
Pic-related should give you a basic idea.
