Bait apps are software programs that may be downloaded for free but contain options for purchasing game currency or virtual currency that extend the game in some fashion. The game is free, but users must pay in order to play for an extended period. Hence, players are enticed to "take the bait" and shell out real dollars to play a game that is advertised for free.
The distribution of free apps that promote in-app purchases has become embroiled in a legal and ethical debate. The practice smacks of deceit - or at least an unethical practice - because there is some question as to whether such an app can be advertised or promoted as free in the first place.
Techopedia explains Bait Apps
For example, the intent of a game app might be to raise fish in a virtual aquarium. The player can buy more food for the fish to extend the game. Clearly, these types of software programs are severely limited without additional purchased options. Also, many such apps are oriented to younger consumers who might not have the consumer awareness to know they are being taken.
There is also a significant legal argument behind the transactions promoted by bait apps. For a contract to be legal, the parties to the contract cannot be tricked into agreeing to its terms. When the apps are promoted as being free, are they inducing those who use them into an agreement with terms of which they're not aware?