Salad drainigeA colander is a fairly simple device - a bowl with holes in to let water (but not prodce) out, a stand to keep it level and allow convenient drainige.
A good colander should not have too many small holes - or it can become tricky to clean.
Why dry salads?Salads fairly obviously need washing - but they also benefit from being dried again.
Additional water dilutes and often wastes any salad dressings used - leaves one fishing around in a puddle at the end of the salad, means spillages are more problematical - and increases the rate of decay of the salad if any attempt is made to store it.
Salad spinningMaybe one day I'll get a salad spinner - to more effectively dry my salads. However, currently my impression is that salad spinners hardly seem worth the trouble. I reckon I'm currently better off with a good colander.