You've got what's called a "monkey wrench," an adjustable-jaw wrench. Versions are still made, but they're kind of specialty wrenches now; the more common version is often called a "Crescent" wrench, after one of the major manufacturers of the design (if you're new to using tools, or your area uses a different term for crescent wrenches, this is what I mean):
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Also known as an adjustable wrench, but that's a bit vague.
You've got a good one: the jaws pinch closed at the tips, rather than splaying out. Many monkey wrenches are made from iron or steel that's not spring-tempered, and frequent use will lead to the jaws splaying out, making for frustration.
One of the sad-but-all-too-true sayings about any kind of adjustable-jaw wrench is that they're perfect for rounding off nuts. A splayed monkey wrench is especially good at this task.
Hold on to it. You may use it infrequently, maybe even never; but if you ever encounter a really large nut/bolt that needs turning, this is a good tool for the job.
