Google Play is probably the largest content store around, and has a host of Android content available, both free and paid, including apps, book, games and videos. Access to Google Play greatly increases the amount of content that can be installed on a tablet.
The nabi DreamTab does have access to Google Play, although children themselves cannot access it, as it is blocked by the parental controls. Instead, parents need to sign in to Mommy/Daddy Mode and from that use Google Play and select any apps or other content they wish to purchase. Once purchased, this content then needs to be made available to children in nabi Mode.