Planning Poker, a.k.a. Scrum Poker, is a consensus based technique to estimate and plan development goals in agile teams.
In a typical Scrum Poker session, members of the team make estimates by playing cards upside down instead of saying them out loud. When all members have their estimates ready, cards are revealed all at once and estimates are then discussed amongst the members of the Agile team.
This is an online version of the estimation cards deck.
It's possible your device doesn't support the HTML 5 feature used to detect if it is moving. In that case, simply click/tap on the flipped card to reveal its value.