The text-to-image model that started the open-source generative-AI wave. Continues as the foundation for AnimateDiff, ControlNet, LoRA fine-tunes, etc.
From Wikipedia
Stable Diffusion is a deep learning, text-to-image model released in 2022 based on diffusion techniques. The generative artificial intelligence technology is the premier product of Stability AI and is considered to be a part of the ongoing AI boom.