I should have mentioned lens filters before. There are many types for different purposes. Mainly they either protect your precious lens or add function for a specific shot. You can read more about them at Photography Life.
On my 50mm f1.8, I have a Tiffen 49mm UV Filter. At one point, UV filters would protect the camera sensor from harmful UV rays but today all DSLRs have built in protection. The label simply persisted.
I chose a clear filter so it won’t have any effect on my photos and Tiffen is a reputable brand. That said, I got it primarily to protect my lens from dust, scratches, fingerprints and the like which is why I keep it on all the time. The Canon lens cap fits right over the filter so it’s completely painless. And it’s just $8! Be sure to pick the right size for your lens.