Confused with inbound/outbound ACL

[lifebook567]

"Access list applied to inbound traffic filter packets before the routing decision is made. Access lists applied to outbound traffic filter packets after routing decision is made" What does it mean? How to choose when to use inbound or outbound? I remember that in some case there is no different either using inbound or out bound, right? Can someone give an example? I?m confused. Inbound and outbound are just the direction of the packet or what?

[pkhatri]

Inbound ACLs affect packets coming into the router from an interface.

Outbound ACLs affect packets leaving the router through an interface. They do not affect packets originating from the router, though.

Both directions are from the perspective of the router itself.

Paresh