Bluetooth Low Energy brought two core specifications and every Low Energy profile is supposed to use them. Attribute Protocol and Generic Attribute Profile.
Attribute Protocol is a low-level layer that defines how to transfer data. It identifies the device discovery, reading and writing attributes on a fellow device. On the other hand, Generic Attribute Profile is built on the top of ATT to give high-level services to the manufacturer implementing LE. These services are basically used to manage the data transfer process in a more systematic way. For example, GATT defines if a device's role is going to be Server or Client.
An interesting thing about ATT and GATT is that they are ...
