Question: I was trying to understand what is the difference between process and thread and I understood all the important points but I was not able to understand this line:

> 
> The typical difference is that threads (of the same process) run in a
>  shared memory space, while processes run in separate memory spaces.
> 
> 
> 

Here is the [reference](https://stackoverflow.com/a/200473/663148).

Can anyone help me understand what does memory space means here? And what does above line means in layman terms so that I can understand?

Answer: 
If all memory in a system is a stack of paper. And each process is a little boy or girl who has it's own pile from the stack of papers on which to do their artwork. These are your applications.

Now if some of these applications are threaded, think of it like being two little girls or boys working together with the same pile of papers. They are both scribbling their creations on the same pieces of paper given to them. While other little girls and boys are not sharing their papers with each other, they are independent - single threaded.

In other words, two threads can read from the same memory and access the same global variables. i.e. memory is shared because it's the same address space.

Separate processes can't do that, they are independent of each other.
In the specific context of Java, a single invocation of Java, starting one JVM (Java Virtual Machine), is one process; code in the JVM has access to memory in that JVM, but not in other JVMs.

Within each JVM there can be multiple threads. These threads share one memory space in the sense that they can access objects created by other threads in that same JVM. They cannot, however, access objects created by threads in other JVMs, since those objects are in the other JVM's memory spaces.