How are threads different from processes?

Like processes, threads are a mechanism that permits an application to perform multiple tasks concurrently. A single process can contain multiple threads. All threads are independently executing the same program, and they all share the same global memory, including the initialized data, uninitialized data, and heap segments.
Sharing information between threads is easy and fast. It is just a matter of copying data into shared (global or heap) variables. However, in order to avoid the problems that can occur when multiple threads try to update the same information, we must employ some synchronization techniques.
Thread creation is faster than process creation—typically, ten times faster or better. On Linux, threads are implemented using the clone() system call.