Start "independent" process in Batch script

When writing bash scripts (linux) you can start a process that will allow the script to keep running (and not wait for the program to finish), but using "&" after the program name

EX.

firefox &

Is there any way to do the same thing in a batch script (windows)?

I presume you want it to run and you still be able to perform commands from the same command line prompt. If this is so, the simple answer is no, as batch scripts still run through dos (or some form of dos shell, which cannot multi task).

Use the cmd.exe start command (note that this isn't in 16-bit command.com of older operating systems).
> start /?
Starts a separate window to run a specified program or command.

START ["title"] [/Dpath] [/I] [/MIN] [/MAX] [/SEPARATE | /SHARED]
[/LOW | /NORMAL | /HIGH | /REALTIME | /ABOVENORMAL | /BELOWNORMAL]
[/WAIT] [/B] [command/program]
[parameters]

Since there is /WAIT, the implication is that not waiting is default operation.

Eg.
start cmd /c dir
Will create a new console window, which will run the "dir" program and then exit. But you'll see the prompt return in the current window long before that finishes.