If any of your tickets say a railcard is required, then you’ll need to have that railcard with you when you travel, so you can show it to a ticket inspector if they ask.
Travelling with multiple passengers
If you have purchased tickets for more than one person, between you, you may need to have more than one railcard.
For example, in the above screenshot, it would be necessary to travel with two 16-25 Railcards.