Describe the difference between a Thread and a Process?

A Process is an instance of an running application. And a thread is the Execution stream of the Process. A process can have multiple Thread.
When a process starts a specific memory area is allocated to it. When there is multiple thread in a process, each thread gets a memory for storing the variables in it and plus they can access to the global variables which is common for all the thread.

Eg.A Microsoft Word is a Application. When you open a word file,an instance of the Word starts and a process is allocated to this instance which has one thread.