Your Spotify artist URL is where your Spotify artist page lives - a fan can use it to find you on Spotify and find all of your releases, and it can be used to extract valuable data on how your fanbase is growing.
To find your Spotify artist URL:
Open your Spotify app
Search for your name on Spotify
Click on your profile name
Once on your profile, click the 3 dots below your name
You should see an option to "Share"
Once you select "Share", click "Copy link to artist"
Your URL should now be copy / pasteable, it'll look something like this:
https://open.spotify.com/artist/0iEtIxbK0KxaSlF7G42ZOp?si=kAQezKA1RyijOfHg4TN9xA
