The Semantic Idle Scheduler is a part of Semantic that performs various operations while Emacs is waiting for user input (idle time). Its primary job is to perform buffer parsing during idle time. You can also use the Idle Scheduler to display function prototypes (see Idle Summary Mode) or symbol completions (see Idle Completions Mode).
This command toggles Semantic Idle Scheduler mode in every Semantic-enabled buffer. This minor mode ensures that the buffer is automatically reparsed whenever Emacs is idle. If there is additional idle time, it runs jobs scheduled by other parts of Semantic, such as Semantic Idle Summary mode (see Idle Summary Mode) and Semantic Idle Completions mode (see Idle Completions Mode).
The value of this variable is the amount of idle time, in seconds, before the Semantic idle scheduler activates. The default is 1.