Have you booked a concierge cabin? If so, then concierge requests are requests for things like a cabana or Palo reservations, etc. that shoreside can book for you before you board. It also means things you can ask your concierge host to get for you on board.
If you booked a non concierge cabin then you don't have to worry about the term concierge request as it doesn't relate to regular cabins.
Normally there are no free upgrades. If you request an upgrade
DCL will expect you pay for that upgrade. It is just about impossible to get an upgrade (free) to concierge.
At the terminal during the check in process you can ask if there are any paid upgrades available...ex. inside to oceanview or oceanview to veranda or any cabin to concierge level and the price will be less than if you booked prior to getting to terminal. Paid port upgrades are not always available.
MJ