Salla ...
A split is where you work your whole body in a cycle of 2/3/4 days (I do 3).
You pick body areas which work together (eg your shoulders and the backs of your arms) and put them into groups, and work them together, so that you can exhaust them in one session. In your next session, you work body parts that are not sore from the previous workout.
I change my routine so that my body doesn't get complacent.
So my current split is:
Gym day 1 ...
Treadmill and stamina machines
+ toning exercises for
Chest
Back of arms
Shoulders
Thighs
Gym day 2 ...
Treadmill and stamina machines
+ toning exercises for
Back
Front of arms
Lower legs
Hamstrings
Gym day 3 ...
Treadmill and stamina machines
+ toning exercises for
Bum
Tum (the toughest bit)
Gym Day 4 ...
(Back to Day 1 ...)