NFT royalties are automatic payouts to the creators of an NFT made on secondary sales. Total royalty percentage is the percentage of these secondary sales that will be payed to the creators of the NFT as a whole. For instance, if an NFT is sold for 100 SOL and the total royalty percentage is 4.2%, then the royalty payout will be 4.2 SOL. This payout can then be distributed amongst the creators by specifying the Creator Share.