Dreams are still a mystery to scientists and researchers. Whether we’re talking the good kind (you’re living in a mansion) or the scary kind (a killer is chasing you through the woods), the causes of dreams are still enigmatic. Experts do have some theories about why we dream, though, and most of them say dreaming is in some way beneficial.

One theory suggests we dream to remember information we learn during the day — one experiment found that subjects who dreamed of the maze they were tasked with completing that day completed the maze much faster the next day than those who had not dreamed of it.

Another theory suggests the opposite: that we dream to forget. Our brains make tons of neural connections during the day based on everything we do, see, touch, and experience. Some researchers believe that during sleep, and specifically REM sleep where dreams occur, our brains review the neural connections made through the day and dump any unnecessary ones.

There are plenty more theories in the video above, including that dreams are responsible for keeping our brains working, and that we dream to fulfill our own wishes.