There are a number of ways of searching and filtering clips.
Use the Quick Search field on the toolbar to filter the clips shown in the main window to those containing the keywords you type in. As you type more characters fewer clips are shown. (The Quick Search field works by searching the clip's name, notes, bin name, user columns, and metadata fields for each word you type in in turn.)
For more advanced searches you can use the Find command to search for clips based on one or more particular clip properties. You can either move to the next clip that matches the query or use it as a filter so that only those clips matching the filter condition are shown in a window.
A query or filter can have different types of conditions, all of which must be true for a clip to match:
When searching you can move forward to the next clip matching the conditions, or search for all clips in one go (all clips that match will be selected). You can also create a new view containing just the matching clips.
When a filter is in effect only the clips that match the filter are shown. Press the filter button (or use the View > Filter... menu command) to toggle a filter on and off. You can also save named queries and then select a named filter to apply from the drop down list in the toolbar (Professional Edition only).
Grouping and Hiding clips are two other ways of excluding clips from being shown in a window, separate from and in addition to the regular filtering mechanism.
See the page on the enhanced query dialog for details of an alternative query dialog available in the Professional Edition.