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 WebP?

Google's format for the web, and a genuine improvement on both of the formats it replaces: lossy like JPG or lossless like PNG, transparency either way, and usually about 30% smaller. Every current browser reads it. Software that stopped being updated around 2019 often doesn't.