system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What's the functional different between different types of image files?

What's the actual difference between JPG, BMP, PNG, TIFF etc?  I know how a GIF is different.  It moves, right?

Edit:  thank you very much.  These are very helpful answers.
gpt
BMP is the most basic one. It contains basically a list telling what color each pixel is in a predefined succession. It needs little processing to go from the device's memory to the display, but being generally uncompressed (or weakly compressed without loss) the file size is quite high.

GIF and JPG were all over the place in the 90ies, being some of the few formats browsers could handle. They had specific use cases based on their characteristics.

GIF can move, doesn't have to. Its main usage in the early internet was for graphics (as in not photos but more like drawings, fancy text, graphic elements like arrows). This because it has a low max number of colors (however, transparency is supported) and uses a lossless compression that takes advantage of large areas with uniform colors.

JPG, on the other hand, specializes in photographs and complex, colorful, photo-like art. It can dramatically reduce the file size of an image compared to the same image in BMP. To do that, it uses a lossy compression that divides the pic into squares and compresses those. The higher up you crank the compression, the smaller the file becomes, but also the more obvious the squares and the degradation of the image become.

TIFF is a complex format that allows for a lot of specialties. It can contain multiple images, sometimes layers, different coding algorithms (mostly lossless). It was (don't know if it's still the case) often used for exchanging graphics with print shops because it allows for a large amount of colors, also in the CMYK format (others often use RGB).

PNG is somewhat the successor to GIF and, to a certain degree, shares its applications. It supports a much larger number of colors, so it ends up being used for large photos much more than GIF. It uses lossless compression.

BTW, lossless means the image can be reconstructed from the file exactly as it was before being compressed. Lossy is when more or less obvious, irreversible changes to the image are done to reduce the file size.