In general, the ring does exactly what it says in the tooltip, which for reference I attach below:
In is usually handed to you when you first spawn in the world, but some modpacks change that to a checkmark quest or something of that kind. You put it on, you can't take it off, stays with you on death, you get a bunch of permanent debuffs, but also a bunch of benefits.
Here's a brief practical explanation of each curse and blessing of The Ring of the Seven Curses: