There's a space between the dot and the script name.
The dot is a shortcut for the "source" built-in command. "source" reads the commands in the shell script into the current shell and executes them. Executing a script directly (i.e., your option B) launches a separate instance of the shell, which then executes the script. In option "A", variables set by the script will persist in the current shell; in option "B", nothing that happens in the script will affect the current shell.
The "source" function is used a lot for things like picking up configuration data for use by a calling script - especially in places like the /etc/init.d scripts in Red Hat/Fedora Linux where they designed the system to separate the updateable script code from the user/system-specific data.
By using a sourced script instead of a config file, the calling script is relieved of the need to parse the configuration definitions and assigne them to working variables - the shell does it.
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