An on-card auto is exactly what it sounds like — the player signed directly on the card itself, pen to cardboard. No sticker, no label, no middleman. Just the player's hand touching the same card you're holding.
Most collectors prefer on-card autos over sticker autos because the connection feels more authentic and the aesthetics are cleaner. There's something about seeing ink flow naturally across the card's surface that a sticker just can't replicate.
Generally speaking, on-card autos carry a premium over sticker autos in the secondary market. Both are prized, but if you've got the choice, on-card is the one that's going to turn more heads.