The Infamous Dots... Help!

[MrBojangle1]

I've not a clue what this does... The dots next to blocks etc..

For example:

PHP Code:

require("./global.php"); 


What's the dot (.) do?! I see many scripts use this, in front of strings etc. For another example:

PHP Code:

$templatesused.=',pagenav,pagenav_curpage,pagenav_firstlink,pagenav_lastlink,pagenav_nextlink,pagenav_pagelink,pagenav_prevlink'; 


The dot just after $templatesused.

Any explanation would be appreciated.