They have manual install instructions [0], and judging by those, what it does is set up a SystemD service that automatically runs on startup. But if you're just looking to play around, I found that downloading [1], making it executable (chmod +x ollama-linux-amd64), and then running it, worked just fine. All without needing root.

[0] https://github.com/ollama/ollama/blob/main/docs/linux.md#man...

[1] https://ollama.ai/download/ollama-linux-amd64