Actual meaning of ‘shell=True’ in subprocess

I am calling different processes with the subprocess module. However, I have a question.

In the following codes:

callProcess = subprocess.Popen(['ls', '-l'], shell=True)

and

callProcess = subprocess.Popen(['ls', '-l']) # without shell

Both work. After reading the docs, I came to know that shell=True means executing the code through the shell. So that means in absence, the process is directly started.

So what should I prefer for my case – I need to run a process and get its output. What benefit do I have from calling it from within the shell or outside of it.