noob questions about some blueprints blocks

GetActorRotation - does it return direction of actor’s sight?

No. it gives you rotation of actor. Each actor has forward, up, and right vector (those red, green and blue arrows). This node gives rotation of this set of arrows basically.

It just happens that camera is oriented along forward vector, so for camera it gives actor sight direction. But saying it gives sight rotation of any actor can be misleading and confusing.

GetActorTransform - what does it means “return transform from actor”?

a Transform is the Set of:
Location: Current position
Rotation: Current allover Rotation
Scale: XYZ scale of the Object