What is BMP?
The Windows bitmap, which stores pixels raw with no compression worth mentioning. Files are enormous. It survives because it's trivial to read - if you're writing an image loader from scratch or feeding an embedded display, BMP is the format that needs no library.
What is TIFF?
The format print shops, scanners and archives run on. Lossless, capable of holding several images in one file, and old enough that everything in that world reads it. Files are large, which nobody in print has ever minded.