Simplify the following text for a Grade 11 native English-speaking person.
Original: The key concept of OoO processing is to allow the processor to avoid a class of delays ( termed : `` stalls '' ) that occur when the data needed to perform an operation are unavailable .
Simplified: The key concept of OoO processing is to allow the processor to avoid a class of stalls that occur when the data needed to perform an operation are unavailable .