Why should I use a thread vs. using a process?

Question

Separating different parts of a program into different processes seems (to me) to make a more elegant program than just threading everything. In what scenario would it make

Answer 1

Came across this post. Interesting discussion. but I felt one point is missing or indirectly pointed.

Creating a new process is costly because of all of the data structures that must be allocated and initialized. The process is subdivided into different threads of control to achieve multithreading inside the process.

Using a thread or a process to achieve the target is based on your program usage requirements and resource utilization.