Formatting the snippet using BBCode to make it easier to read...
if [ -f /etc/file ];
Yes, the . performs the same task as source (see the bash manual page and look for the section "SHELL BUILTIN COMMANDS"). The semicolon here is part of the syntax for the if statement (again see the bash man page --- it's described under "SHELL GRAMMAR" and is towards the end of the sub-section titled "Compound Commands").
The if statement above simply checks that /etc/file exists and is a regular file, and if it exists, then it sources it.
Hope that answers your query!