Test Bad ;- 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 Tab :-

Test Bed: Preparation of sheet (excel) which contains the 
accurate test data for each and every test cases which are 
to be executed.

Test Lab: These will purely an execution level where the 
test cases identified will the executed and status will be 
updated.

Test Environment: This talks either Integration or System 
or UAT environment for executing purpose.

Test-bed & test Environment are same, the tools,environment 
all the Supporing element used to Conduct Testing .

Test -Lab: No idea.