Exec vs ExecWait vs ExecShell vs nsExec::Exec vs nsExec::ExecToLog vs nsExec::ExecToStack vs ExecDos vs ExeCmd

Can I know what are the differences between each Exec, ExecWait, ExecShell, nsExec::Exec, nsExec::ExecToLog, nsExec::ExecToStack, ExecDos and ExecCmd, as in when to use which?

I 've posted the various execute calls I know. I am trying to make a comprehensive list, so that it helps future visitors..

1. Exec: Plainly execute the called string, be it some application, console or file.

2. ExecWait: Executes like Exec but waits till the process exits.

3. ExecShell: What is it for?

4. nsExec::Exec: Just like Exec or ExecWait but only for command prompt and that too without opening the console window. I am unsure if it waits for process to exit. Does nsExec::Exec wait for child process to exit?

5. nsExec::ExecToLog: The documentation says ExecToLog is similar to plain nsExec but it outputs to log window. What does that mean, what is a log window?

6. nsExec::ExecToStack: The documentation says ExecToStack is similar to plain nsExec but it pushes output to stack. I get that.

7. ExecDos: Same as nsExec::ExecToStack but it additionally (Is it not?)

   a. takes string parameter that serves as stdin for running application.

   b. works in both sync/async mode.

   c. it works out of section - for .onInit check outs.

8. ExecCmd: Same as ExecDos but it doesn't require these

   ExpandEnvStrings $3 %COMSPEC% 
   ExecDos::exec  /C 
   

   parts. Am I correct?