[tcas]

There's a few hard/soft products that are grouped as premium economy.

On domestic flights there's "Comfort" seats, which give you more legroom (and free snacks and drinks on US domestic flights). On international flights "Comfort" seats still exist, but on some flights there's true premium economy, which does have wider seats (e.g. the A350 on Delta's fleet is 2-4-2 seating in premium economy vs 3-3-3 in coach).

You get better meal service (my experience on Delta is it's plated and brought out in a similar fashion to domestic first class) and domestic parts of the journey will sometimes book into first class.

Comfort pricing is usually $50-150 more per leg vs coach. Premium economy is usually somewhere in between coach and business, leaning a bit more towards the coach side.