From the publisher's website:
These stand-up, miniature table tents help parties to keep track of the spells that are up, and what bonuses that they give to the players. This set contains many of the more useful individual arcane buffs, i.e. Fly, Mage Armor, Bull's Strength, and nine more of D&D 3.5's most useful group spells/abilities.
We designed this set after repeatedly having people miss attacks or saves because they forgot about bonuses that they had. It makes it alot easier to have a stand that shows that you can't grabble the PC because he has Freedom of Movement up.