system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is a WEBP file, and how does it differ from a JPG?
gpt
WebP aims to replace the most popular image formats.

WebP can, like JPG, use lossy image compression techniques: by discarding some information from the original image, the file size can be much smaller; the more information is discarded, the smaller the file gets.

Sometimes just slightly reducing the image quality makes a large difference on the file size, while to an untrained eye the image looks as good as the original.

Because JPG dates back from a long-gone era, there are now better compression algorithms that were developed, and computers are now fast enough use those algorithms.

WebP can also be used as a lossless format; typically replacing PNG.  It can also do animation; typically replacing GIF.

One thing to note: conversion between lossy formats (from JPG to WebP, or from H.264 to H.265, or from MP3 to AAC) is seldom a good idea: there is loss added each time there is a conversion.