JPEG
JPEG - Joint Photographic Experts Group (acronym for the group that created the standard)
JPEG
In computing, JPEG (seen most often with the .jpg extension) is a commonly used method of lossy compression for digital photography (i.e. images). The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and image quality. JPEG typically achieves 10:1 compression with little perceptible loss in image quality, and is the file type most often produced in digital photography or computer screenshots. The file type also is prone to pixelating when an image is shrunk.

Lossy Compression:

In information technology, “lossy” compression is a data encoding method that compresses data by discarding (losing) some of it. The procedure aims to minimize the amount of data that needs to be held, handled, and/or transmitted by a computer.
Reference
Wikipedia
Image File Formats
GIF
JPEG
PNG