When I open file with
gedit templates/index.html
I see this in terminal and can't use it more:

How can I open file in text editor without blocking terminal?
When I open file with
gedit templates/index.html
I see this in terminal and can't use it more:

How can I open file in text editor without blocking terminal?
You will enter the & to instruct the shell to launch Gedit in the background:
gedit templates/index.html &
"After the fact", i.e., after you forgot to enter the &, you still can send it to the background.
bg to send the stopped process to the background. Otherwise, Gedit will remain "stopped" appear as frozen.