Project Organization, searchable keywords and tags in Adobe Premiere
Keywords are an optional field of the project panel. In order to view or add keywords, you need to set the project panel to List View (you can switch between List View and Icon View with the buttons in the lower left corner).

In the flyout menu of the project panel, select Metadata Display… to customize the columns of the list view to show whatever information you want it to. You will find the keywords in the category Dublin Core. Check keywords and click ok. You might have to resize the project panel (or remove the columns you don't need from the Metadata Display menu) in order to see the keyword column. You can rearrange the columns using drag-and-drop. Once you have added some tags to your clips, you can search for clips with specific tags using the search function of the project panel.

There's also some more useful metadata columns hidden in that menu that are not shown by default that you might find useful. For example, the category Premiere Pro Project Metadata has the entries Video Usage and Audio Usage that show you how many instances of a clip exist in your sequences in your current project. There are also fields for Comment, Description, Scene, Shot and much more. Using the Metadata Display menu, you can customize the metadata columns to only show those that you need for your workflow.