It is a Wagner–Meerwein rearrangement. Your particular example has the following mechanism:
Edit: Regarding your comment, the best way to see what is happening is to draw the product so that it resembles the reactant (like in the image below) and then in another step draw it in a more reasonable conformation:
Related to followup question in comment:
The molecule is redrawn from a different orientation.
This ring system is bicyclic and is basically a five-member ring stitched to a five-member ring stitched to a six-member ring. The original six-member ring is shrinking to a five-member ring and one of the original five-member rings is expanding to the new six-member ring.
Track where the geminal dimethyl groups are, they do not shift. This will help you sort it all out