A polygon (which is straight-sided) is concave if there are “dents” or indentations in it.
You can remember it by con-“cave” (it has a cave in it!)
A machine that can be programmed to do things with data.
Computers can usually:
* “input” data from a mouse, keyboard or touch-screen,
* “process” the data using a CPU and memory, and
* “output” the result onto a screen or save it to disk.
Computation is finding an answer by using mathematics or logic.
You can use a computer to do computations.
But you can also do computations yourself when you add, subtract, multiply, etc.