Lets first understand what is the meaning of Software testing. In simple wards we can say that Software Testing is an process of executing a program or a process or a system with the intent of finding errors, validating against requirements or specifications.
Now coming to the the STLC the we can divide it into following six phases -
1. Initiation Phase
2. Planning Phase
3. Test Case Design Phase
4. Test Case Execution Phase
5. Test Case Reporting
(all of the above is self explanatory)