Both wood and composite can scratch, though the tendency is higher in wood than in composite. Moving furniture or heavy play is the primary cause of scratches on decking boards. The solution varies with the manufacturer and type of scratches.
While scratches might make your deck ugly, it is advisable not to repair them because, over time, they blend in with the rest of the deck. However, your composite deck has a noticeable scratch use a soldering iron to level the scratch as well as blend it with other parts of the deck.
Alternatively, you can touch up small scratches, and scuffs use a tough-up concealer.
For wood deck boards, you can paint or stain the deck.
For deeper scratches or substantial damage on the deck, a replacement me be required.