JPEG

A comparison of JPEG quality, at 1, 50, 90 (default), and 100, all taken in 2560x1440 resolution. Note the visual difference between 50 and 100 is almost unnoticable unless viewing closer, but the filesize is roughly ten times as large.

JPEG (more commonly seen with the extension .jpg) is an image format which uses lossy compression to reduce the file size of the image. This results in file sizes that are significantly smaller than uncompressed formats such as BMP or TGA. Lossy compression affects image quality, but higher quality JPEGs will have nearly imperceptible artifacts. JPEGs are suitable for photographs and screenshots, but are not preferred for textures or diagrams.

 Source

Used for screenshots in many games.^[Clarify]