There are this two names: a subshell and a child-shell.
Yes, a child process will be started by any of this:
sh -c 'echo "Hello"' ( echo "hello" ) echo "$(echo "hello") echo "hello" | cat
Are all equivalent and share the same name? Do all share the same properties?
POSIX has this definition:
A shell execution environment consists of ....
But the last paragraph of above link has this:
A subshell environment shall be created as a duplicate of the shell environment, except that signal traps that are not being ignored shall be set to the default action.
Command substitution, commands that are grouped with parentheses, and asynchronous lists shall be executed in a subshell environment. Additionally, each command of a multi-command pipeline is in a subshell environment; ....
sh -c 'echo "Hello"' is not included there, should that be called a subshell also?