Difference linq and plinq

Question

What is the difference between these two?

What is the best way to compare ?

It is always better plinq ?

When we use plinq ?

Answer 1

Consider avoiding anonymous types while working with PLINQ because according to Threading in C#, by Joe Albahari:

anonymous types (being classes and therefore reference types) incur the cost of heap-based allocation and subsequent garbage collection.

(...)

stack-based allocation is highly parallelizable (as each thread has its own stack), whereas all threads must compete for the same heap — managed by a single memory manager and garbage collector.