Marketing card

Marketing cards or ad cards, not to be confused with promotional cards, were added to the contents of a booster pack from Tenth Edition on. This sixteenth card is in the booster packs because the Magic Brand team has discovered that for some players the only way to reach them with advertising is through booster packs. The advertisements are about Magic-related things and are meant to educate newer players on the many other aspects of Magic.

Description
The cards exist in the booster packs because marketing pays for them. The Brand Team allows R&D to place content on one side of the cards, there they place content such as a game concept relevant to the specific set (called "Tips & Tricks", or a Rules card), links to useful sites, and tokens. Because R&D uses “their side” for several different items, and since all tokens are on that side, not every ad card has a token.

The quality of marketing cards is slightly less than that of regular cards.

Occurrence
While being an approximation, the expected ratio of token cards to other cards is:
 * 1 out of 3 for core sets.
 * 2 out of 3 for expert-level sets.

Battle for Zendikar onwards
The ratio between token cards and other marketing cards was shifted heavily in favor of tokens in Battle for Zendikar. The new ratio is "approximately 9:10".