STLC is software test life cycle it starts with

* Preparing the test strategy.

* Preparing the test plan.

* Creating the test environment.

* Writing the test cases.

* Creating test scripts.

* Executing the test scripts.

* Analyzing the results and reporting the bugs.

* Doing regression testing.

* Test exiting.

SDLC is software or system development life cycle, phases are...

* Project initiation.

* Requirement gathering and documenting.

* Designing.

* Coding and unit testing.

* Integration testing.

* System testing.

* Installation and acceptance testing. " Support or maintenance.