What is a relapse exactly?

Been free for 20 days now, today the urges hit pretty hard after gym and I quickly searched on twitter for something, edged like 2 mins and realized the fuck I'm doing and stopped

Pretty new here so I'm always wondering what exactly a relapse is? PMO? Or just my incident already?

I know days or streaks do not matter since it should be a permanent lifestyle change but I'm curious nonetheless if that makes sense!