Inside: Bluetooth Low Energy

Defines the "who's who." It determines if a device is a Central (like your phone) or a Peripheral (like a heart rate sensor).

This is the most important part for developers. It defines how data is exchanged using a hierarchy of Services and Characteristics (e.g., a "Battery Service" with a "Level" characteristic). Inside bluetooth low energy

The Host acts as the software stack that manages how data is structured and secured. Defines the "who's who

Handles the "raw bits" and frequency hopping across 40 channels to avoid interference. The Host acts as the software stack that

Handles pairing and encryption to keep the data stream private. 3. The Application (The "User Interface") BLE with ESP32 tutorial part 1: the Server

This is the hardware layer responsible for actually sending and receiving signals over the 2.4 GHz band.

The "brain" of the radio. It uses a state machine to manage whether the device is Advertising (broadcasting its presence), Scanning (looking for others), or in a Connection state exchanging data. 2. The Host (The "Brain")