Summing numbers

Sorry probably a very simple question but could somebody please look at the following piece of javaScript and explain to me what the ++ does, I know it is used for summing numbers but what does it mean?

for (count = 1; count <= biggestNumber; count++)

I am only starting out in javaScript so bear with me.

Cheers Stu

The count++ increments count by 1 until count is less than or equal to whatever value biggestNumber contains.

Thanks for your help