What are process and thread, and what are their fundamental differences?

A process is an isolated unit of program execution with its own address space, resources, and state. A thread is a lightweight unit of execution within a process that shares memory and resources with other threads of the same process.

Main differences:

• Isolation: processes are isolated from each other, threads are not.
• Memory: processes have separate address spaces, threads share the process's memory.
• Creation: creating and switching between threads is faster than between processes.
• Communication: processes communicate via inter-process communication (IPC), threads communicate directly through shared memory.

In Go, instead of threads, goroutines are used — very lightweight threads managed by the Go runtime, which allows efficient utilization of multithreading.