Both Keywords and Filters provide you and your users with easier ways to find the relevant information they need.
Keywords are commonly used on images, especially due to the metadata extraction feature of the platform, and are usually used to describe the image in question - whereas Filters come in handy as an easy way to categorise your files.
You can tag your Resource files with Keywords as they get added into the system, or when editing them, at which time you can free-type in any words that describe the file or image that you think other users may use to locate it.
You can also set up Global Keywords via Admin > Settings. This is useful when there are select words that might regularly be applicable against your files. Once set up in the Admin section they then do not need to be typed each time you add a file - they can then easily be selected from the Keywords dropdown.
When uploading images, any keyword metadata embedded in them can automatically be carried across to the platform via the [meta_keyword] command. These can be added in conjunction with any free-typed or Global keywords.
Users can then enter keywords in the Search or Advanced Search on the platform to easily locate these files.