Image optimisation is very important for video games. There are a few different ways you can optimise an image, but there are 2 types of optimisation file types, 'Lossy' and 'Loss-Less'.
Lossy file types make the file size smaller, but at the cost of losing some pixels, which reduce the image resolution. Sometimes this resolution loss isn't very noticeable so in some cases lossy files are better. The most common file type that is lossy are JPEG images.
The other type of optimisation is loss-less. This is where none of the pixels are lost, meaning the image resolution is exactly the same as when the image was generated. Loss-less files are much better than lossy because the integrity if the image is not damaged, meaning if it was a texture for a game at 2048x2048 resolution, that texture will be applied to the 3D Model at exactly 2048x2048 pixels. A common loss-less file type is PNG.
