What are .mrc files and how do we interpret them?

I was preparing ground truth for protein particles and exported the result which eventually helps me to get .star file of true particles. Apart from that I found .mrc file quite initeresting, but I don’t know that this file is. There are individual .mrc files generated for each input micrographs.

Could anyone please tell me what are these .mrc files that I got as a result of exporting 2D calsss job in cryosparc? How do we interpret these little silver-colored chunks in the image?

A sample image of .mrc file is included here: