What is Re-Testing and Regression Testing?

Re-testing : Retesting means we testing only the certain part of an application again and not considering how it will effect in the other part or in the whole application.
Regression Testing :Testing the application after a change in a module or part of the application for testing that is the code change will affect rest of the application.

What is Test Bed?

Test Bed is an execution environment configured for software testing. It consists of specific hardware, network topology, Operating System, configuration of the product to be under test, system software and other applications. The Test Plan for a project should be developed from the test beds to be used.
Test Data is that run through a computer program to test the software. Test data can be used to test the compliance with effective controls in the software.