Correct, it's an in-game timecard that is redeemable for a months worth of play. These retail for $20 each on the EVE website

They can also be traded on the market in-game for ISK.

They do have other uses such as, you can can use 2x PLEX as the fee for transferring a character to another account instead of the card fee.

http://support.eveonline.com/pages/kb/article.aspx?id=495