what is the diffrence between a computer and a computer tower?

The word "computer" is simply generic for what you are using now.

"Tower" simply means the computer stands upright like a tower whereas some are meant to be placed sideways. on your desk. Towers are usually bigger than non-towers.

I think the word "computer" depending on it's actual meaning , means the part of hardware that does the computations ( also know as CPU: central processing unit )

while the computer tower , is the case in which all the components exist like the cd rom, mother board, hard disk, graphic card, sound card ...etc

some manufacturers refer to a computer as a desktop version ( a tower put on its side). Which means its less expandable but cheaper.

Dell and Apple used to do this back in the late 90s. Now I think only Compaq and HP do this.

Computer Tower is just a casing/chassis

Computer is a computing device.