Why do we need STLC if we have an SDLC?

Can anyone please tell me why do we need STLC if we have an SDLC.

STLC stands for Software Testing Life Cycle. Testing now is not only limited just to find bugs but has a wider scope and is required right from the beginning of the project when the requirements are not even finalized.

Since testing is also standardized. Just like development of software has a life cycle (SDLC) , Testing too has a life cycle (STLC). In STLC process, different activities are carried out to improve the quality of the product.