The main character is Zack (James Van Der Beek), who is the rebel of the school, he always gets into a lot of trouble, but because of his wits and the help of his friends he gets out of this trouble.
Zack's best friend is Skreech, a nerd who tries to be cool. Zack basicly pushes Skreech around. But hey, when your a nerd one abbusive friend is better than no friend.
The other male friend of Zack is Slater, in the first series they are rivals for the love off Kelly, but when Zack gets her and Slater gets Jessy they become real friends.
We've got 3 girls in Saved by the Bell: Kelly (the cheerleader), Jessy (the intelligent one) and Lisa (the rich one).
Most of the times they just hang around with the guys, but they also give their input into the situations.
The last main character is Mr. Belding, the principal.
He's basicly a guy who wants to be accepted by the students, but has to be strict with them.
Especialy he and Zack have a love-hate relationship.
The best thing about Saved by the Bell are the situations the main characters get in. They are picked from real life, but are exploded to a level where you can only laugh at them.
The interactions between the characters is also great (especialy Zack and Belding)
This is a show that you just gotta love, even though it's a little bit dated (early nineties...)