What costs Gas in Ethereum?

As a developer and Computer Architect looking into Ethereum, I am really trying to get to the gist of what the cost of Gas is on the system.

Are there instruction costs, like old processors, where certain instructions cost 'more', in terms of Gas, like the clock cycles of the 'hard' processors that have come before?

Simply googling 'what costs gas in etherium' gave me a list of 'Gas Stations', but not the answer I was looking for, so I come here, to Steemit, and see what you can do.