1# Thread Model Overview (FA Model) 2 3There are three types of threads in the FA model: 4 5- Main thread 6 7 Manages other threads. 8 9- Ability thread 10 - One ability thread for each ability. 11 - Distributes input events. 12 - Draws the UI. 13 - Invokes application code callbacks (event processing and lifecycle callbacks). 14 - Receives messages sent by the worker thread. 15 16- Worker thread 17 18 Performs time-consuming operations 19 20Based on the OpenHarmony thread model, different services run on different threads. Service interaction requires inter-thread communication. Threads can communicate with each other in Emitter or Worker mode. Emitter is mainly used for event synchronization between threads, and Worker is mainly used to execute time-consuming tasks. 21 22> **NOTE** 23> 24> The FA model provides an independent thread for each ability. Emitter is mainly used for event synchronization within the ability thread, between a pair of ability threads, or between the ability thread and worker thread. 25