This is called a fire bug (or firebug). It’s also called a fire beetle.
So what’s the difference and which is it?
The beetle and the true bug (as opposed to ‘bug’ which is a sloppy name for anything small with a lot of legs) are both types of insect.
They can be distinguished by their mouthparts and their wing cases.
The creature in the photo is actually a true bug and not a beetle at all.
But given the number of wildly unrelated meanings for ‘bug’, I’m happier calling it a beetle.