Another Stupid Question

I had a cube and i subdived and other stuff.Then I selected half of the cube and pressed X, how come it doesn’t say “erase selected” and sometimes it does?It is driving me insane.

In object mode you will get erease selected because you are working with the whole object.

In Edit mode you will get a selection for

Vertices
Edges
Faces
All
Edges & Faces
Only faces

Because you are working withe the mesh which has many data items that can be erased depending on what you need.