Card is legal to play in any sanctioned tournaments for that format.
If a card appears on the banned list for your chosen format, then you may not include that card in your deck or sideboard. Doing so makes your deck illegal to play in any sanctioned tournaments for that format.
If you wish to use a card that’s on the restricted list for your chosen format, you may include only a single copy of that card, counting both your main deck and your sideboard.
Currently, only the Vintage format uses a restricted list.