Sometimes the Quick Search or even Advanced Search criteria available to you are still not enough to narrow down your search as far as you'd like. Filters on Grid columns are often useful in those cases.
Every column header has a small funnel icon to the right of its heading text. Clicking on the funnel will show you a list of values you can select from, as well as Blanks, Non-Blanks, and Custom filters:
To filter by multiple criteria, or to use operators like Greater Than, Less Than, Starts With, etc. select the Custom option (make sure to pay attention to whether you're using And conditions or Or conditions):