Credit card

I was recently wondering as I was making online transactions. When you shop from a rather random website and you pay via credit card, does the shop owner actually see and have access to your credit card information? Or is it decoded in some way or used in a 3rd party billing security system...

My hp envy is very magnetic at corners. metal objects stick. If I place my credit card or thumb drive, etc. next to the touchpad (which is where magnet is strongest) am I damaging my credit card?