GPUs are specialized computers used to accelerate "Matrix Multiplication". Traditionally, matrix-multiplication was used to calculate 3d objects vs the camera / screen... a very common operation in video games. There's a bit of math and study involved in this, but this picture should give you the idea:

GPUs are designed to perform this operation trillions-of-times per second, because video games have a lot of objects on the screen that move around (rotate / animate, etc. etc.), that needs to be simulated in this manner. So any video game will have a powerful, dedicated computer specifically designed for this matrix-multiplication operation.

About... 15ish years ago, someone created the "Tensor" operation for Deep Learning Neural Networks. This allowed ANNs to be written as a matrix-multiplication problem, and therefore accelerated on a GPU. GPUs after all, are the fastest computers we got for Matrix Multiplication.

GPUs are used in Machine Learning to train Neural Networks. Everyone in the AI field uses NVidia GPUs. Also NVidia uses special machine learning cores in the GPU, Tensor cores, to accelerate Ray Tracing and DLSS. AMD does not have these type of chips on their GPU that’s why ray tracing performance on AMD cards is significantly slower.