Filters work in tandem with Columns to provide you the information you want to see. You can think of filters specifically applying to the content you want to see.
You can apply filters by clicking on the "Filter" icon in the upper left and a pop-up will appear with all the options you can choose from.
You can apply as many filters as you'd like and customize them to cut through the chaff and drill down to see the content that is important to you.
Once you've selected the filters that show you the content you want, simply click on the green Filter button in the lower right hand corner.
You can always see how many Filters are active in a view by looking at the number next to the Filter icon.