Question What's the direction part of a sphere and box cast?

So If you look at a sphere/box cast there a part that says direction. What's this for? If its sphere cast shouldn't it check for everything inside?

 

cast is different from overlapsphere,
so direction is where it "shoots" the sphere, to check for hits. (basically thick raycast)

https://docs.unity3d.com/ScriptReference/Physics.SphereCast.html
https://docs.unity3d.com/ScriptReference/Physics.OverlapSphere.html