I've seen URI before on a few websites but just assume it was meant to be URL. Turns out I was very wrong and I've been using the wrong term for years 😂
https:// = scheme
github.com = host
/tootsuite/mastodon = path
host = URI
path = URI or URN
host+path=URI
scheme+host+path=URI or URL
So if you're asking someone for how to get to their website, what you're really looking for is the URI; you don't want someone to spell out https;//joinmastodon.org, just joinmastodon.org. When you want a full link (like copy/pasted), it's more accurate to say URL but URI is still correct.
Just thought that was interesting ¯\_(ツ)_/¯