The period is a concatenation operator. So say you have your three strings
$string1 = "Hello there, ";
$string2 = "my name is ";
$string3 = "Mike Wilson!";
You could join these three strings together like so:
$joined_string = $string1 . $string2 . $string3;
If you print out the joined string:
echo $joined_string;
The output would be:
Hello there, my name is Mike Wilson!
Hope this helps ya out!
-Josh B