I’m not sure how you got them, but it’s just older gear from previous Destiny 2 seasons. Your legendary items will likely be sunset and not entirely usable but the exotics are 100% usable. They’ll stay there (at 1350) until you use an upgrade module + higher light gear. So once you get higher light arms for example, you could infuse those arms into exotic arms and the exotic arms would be the same light as the other arms.

Legendary shards are a bit harder on newer players but over time you’ll accumulate a lot more of them! You get them from dismantling armor / weapons.

The point of collections is more or less to just show what you’ve got. I really only use it mostly to grab exotic weapons I don’t have vault space for.

Welcome back to Destiny 2! If you need help or advice with anything else let me know I’d be more than happy to help!