What do they mean by "gauge?

#1

In a pattern, what does the “gauge” actually mean?

#2

It’s the tension of your sts, how loose or tight they are. If a pattern suggests 16sts over 4", you should get 4 sts per inch so the sweater or hat will fit you and not be too large or too small. If you get 5 sts per inch and knit the pattern size you think you wear, it will be too small; if you get 3½ sts/inch it’ll be too large. You can use a different gauge, but will have to adjust the pattern, using more or less stitches.

#3

I have these links bookmarked for more info.
http://axesnyarn.blogspot.com/2008/10/i-quite-often-see-people-asking.html
http://www.earthguild.com/products/knitcroc/marypat/gauge.htm