A standard is an ideal or set of criteria that you use to judge things against. Colleges have certain standards for applicants, like a minimum SAT score or an above average grade point average.
If you complain that the soup isn't up to your standard, you're comparing it to an ideal and finding it lacking. (Just don't be surprised if the chef then "accidentally" spills it in your lap.) The economy used to work by the gold standard, where one dollar equaled a fixed amount of gold. A standard can also be a military flag or banner on a pole. Or a popular old song that's considered a classic.