Can anybody explain to me what the file extensions are in Slackware and what they do, in relativeness to Windows? 10 minutes to finish downloading slackware's iso 2 and then burn them and install them as my first ever Linux... Want to just have a basic understanding of what I'm doing before I start it up.

There are two levels (environment) which differentiate the treatment of file extensions.

In Windoze, the operating system keep track of the file extensions and its association through registry. It is very important for Windoze.

In Linux (general), At the Operating system level, it means nothing at all. Linux only keep tracks of ownership and permission of the files not the file extension. Saying this, Linux have a standard filesystem hierachy which you can find the standard documentation from http://tldp.org.

At the xwindow level the file extension does play a role. The xwindow such as gnome have nautilus to do this and many more. It is controlled by MIME settings.

I stand corrected.

ps.
at console level, when we use the command ls, it does take into the account of file extension to apply different colour for different file types.