Test suite is a container that has a set of tests which helps testers in executing and reporting the test execution status. It can take any of the three states namely Active, Inprogress and completed.
A Test case can be added to multiple test suites and test plans. After creating a test plan, test suites are created which in turn can have any number of tests.
Test suites are created based on the cycle or based on the scope. It can contain any type of tests, viz - functional or Non-Functional.