In addition to everything that everyone else has said: I run Ollama on a large gaming PC for speed but want to be able to use the models from elsewhere in the house. So I run Open-WebUI at chat.domain.example and Ollama at api.chat.domain.example (both only accessible within my local network).

With this setup I can use my full-speed local models from both my laptop and my phone with the web UI, and my raspberry pi that's running my experimental voice assistant can query Ollama through the API endpoints, all at the full speed enabled by my gaming GPU.

The same logic goes for my Stable Diffusion setup.