What is the place in the terminal?

Question

linux

The people, I know that the question is painfully simple, but it is not possible to correctly formulate a query in Google.
It's simple...
What is this place in the terminal?

Answer 1

it's not even about gravity, it reacts to any unclosed bracket/quote mark,
it's just a suggestion to the user to end the line and close the bracket

Answer 2

What do you mean what place? there are system libraries, what else?

Answer 3

Vladimir Zhdanov :

Command Substitution
       Command substitution allows the output of a command to replace the com‐
       mand name.  There are two forms:

              $(command)
       or
              `command`

       Bash performs the expansion by executing command and replacing the com‐
       mand substitution with the standard output of  the  command,  with  any
       trailing newlines deleted.