Do these play music or have active noise cancellation?

No. They are passive silicone earplugs that block sound physically. There are no speakers, batteries or electronics.

Are they comfortable for side sleepers?

The low-profile shape is designed to sit flush so the pillow does not press on the ear. Comfort still depends on your ear shape and how deep you insert them.

Yes. They are reusable silicone, so rinse them after use and let them dry. Replace them when the silicone stiffens or tears.

Will they block snoring and airplane noise?

They reduce nearby snoring and cabin noise, but low-frequency engine rumble is harder to block passively. A good seal matters more than anything else.

How do I get the best seal?

Roll or press the plug gently into the ear canal opening until it sits flush. A poor seal lets sound leak past, so try a different angle if noise still gets in.