What is a wipe in Escape from Tarkov?

Taken directly from GamerJournalist, but confirmed from my own personal experience:

Escape From Tarkov performs wipes every so often, which sometimes coincide with various updates to the game. A wipe in Escape From Tarkov is a complete reset of everything on your character. Imagine as if you just bought the game and have very little rubles to work with—that’s the state everyone gets reset to in a wipe.

To elaborate on this, all quest progression and stats are reset as well. It's literally like starting a fresh account in the game for not only you, but every other person who plays the game.

When Battlestate adds new maps, new tasks, new features, or other major updates, they’ll usually perform a wipe. There are many reasons for this, but simply, it’s to put everyone on the same playing field. Also, new items make their way into the game all the time, some of which would never get any usage. Take a lower-level armor, for instance. If you continue to keep your levels, nobody would ever use the new lower-tier stuff since everyone would have the best stuff.

I consistently come back to EFT when wipes happen. It's one of the few times in the game where all players will be on the same level, give or take the benefits (additional inventory space and some extra items) from premium accounts and holiday gifts. Personally, I've found wipes of the game to be the most nerve-racking and exciting, but some would disagree. It allows me to get back into the game when I've had a hectic couple of months IRL and feel as if I'm too behind to catch up to the regular playerbase.