What is the difference between Serail and Parallel Patterns

Parallel patterns are forced parallely (at the same instance of time) @ SI of each flop and measured @ SO. Basically these patterns are used for simulating the patterns faster. Here only two cycles are required to simulate a pattern : one to force all the flops and one for capture.
Serial patterns are the ones which are used @the tester. They are serially shifted and captured and shifted out.