These are titles which provide downloadable content to a specific title. The reason why these titles can only be purchased in game, is because all DLC content is under a set of title(s), downloading via the eShop would download all DLC content. And because all DLC content is under a set of title(s), they are viewed as one(?) title in system settings, and individual DLC can only be deleted from within the game which uses the DLC.
The titleID-low for DLC is: ((uniqueID<<8) | DLC_title_index). DLC_title_index starts at zero. Each DLC item is grouped under a DLC_title_index. Usually an application only has one DLC_title_index, but for applications which have a *lot* of DLC there's more than one DLC_title_index(JPN Home Menu for themes for example).
|00008800||JPN||New 3DS Internet Browser DLC, used for disabling the web filter.||v0|
|00022800||EUR||StreetPass Mii Plaza [DLC]||v5|
|0007AD00||JPN||New SUPER MARIO BROS. 2 [DLC]||v16, v48|
|0007AE00||USA||New SUPER MARIO BROS. 2 [DLC]||v16, v48|
|0007AF00||EUR||New SUPER MARIO BROS. 2 [DLC]||v0, v48|
|00095800||?||?||v0, v32, v48|