I'm at uni beginning a web design course and we are starting to learn HTML 5 and CSS. I have previous experience with CSS and HTML but i haven't built for mobile devices or tablets, only for the desktop.
I don't know loads of stuff, but i understand the basics of the languages but i am stumped with a symbol. Before you say anything, we aren't being taught by the tutor, we are just given worksheets to work through otherwise i would have what the symbol is.
On the mobile device, when it was said about starting the navigation tag - you know, aligning it and colouring it in etc - that's when i came across the "*" symbol.
The code we are to put before the nav id was:

* {
margin: 0px;
padding: 0px;

I've looked on google and everything but can't find an explanation for the "*" symbol.
Would appreciate any response as i'm very curious and would like to extend my knowledge.

That stands for EVERYTHING.
It's a reset to get rid of any different default settings in different browsers, which can differ by a couple of pixies here and there and make your design look different in other browsers. You then have to set every margin and every padding for every other tag as and when you feel you need them, rather than use the default settings.

Thank you for your reply. That's helped :) Is this only used when building for devices other than computers? because we havent been told to put it into our desktop.css file, only mobile.css and tablet.css.