i saw a car with slightly inclined wheels what is the use of it

I presume you mean inclined from vertical
Just think what happens when the suspension is compressed.
In vehicles with independent suspension (ie, without a common axle between the left and right wheels), the wheels will be inclined top outwards at no load, vertical at normal load, top inwards at high load.

There are other issues as well.
Try looking up camber, caster, toe in and trail.
Regards

what is the use of toe in and toe out

Let me tell you from the RC car point of view.(It's less extreme in real life.)

Toe out tends to give the car more steering on corner entry but makes it difficult for the car to track straight. Toe in reduces turn in and overall steering but gives the car better tracking in a straight line.