Wangus,
John Farley gave, what was to me, the most succinct description of wing sweep that I have ever read, in this thread:
http://www.pprune.org/tech-log/46399...ng-theory.html
Take a straight non tapered wing and saw through it at 90 deg to the leading edge.
Now cut through at the sweep angle of your choice.
The two cross sections will have the same thickness but the one with sweep has a longer chord
Hence the thickness chord ratio is less on the swept wing.
Thickness chord ratio determines the speed at which shockwaves form.