What is the use of temporary records and state record in application engine

Temp Tables:
The are used to store the immediate values during the processing of the AE.
They help in batch processing by creating multiple instances and there by facilitating parallel processing.
If used properly they can greatly improve the performance.
State Records:
They are used to pass on values from one section/step/prog to the other.
There can be a max of 200 state rec that can be used in a single AE but only one of them can be default.state record name must end with _AET.