Fractals are a type of mini-dungeon with a difficulty scaling system built in. They scale from difficulty level 1 to 100. They’re pretty much designed for level 80, though in theory you can run them as a sub-80 because it boosts you to 80 while you’re inside. You’re better off in regular dungeons at your level, IMO.
Even though you’re boosted to 80 in a fractal, you will be gimped by not having access to all your skills, not having access to your elite specialization, and likely having inferior gear. A pug might well kick you, though I’m sure you could get guildmates to take you.
Eventually you’d hit an absolute gear barrier: Above difficulty level 20, you need special infusions slotted on your gear, and those slots are only available on level 80 Ascended gear. The higher difficulty level you run, the more infusions you need. Without them, it’s eventually like insta-death.
You can learn more about fractals here: https://wiki.guildwars2.com/wiki/Fractals_of_the_Mists.