When you have enabled Advanced or Micromanage tariff editing modes you are also able to create and edit room/resource features. Room features can be assigned to individual rooms, and in the booking form, if these features have been created and assigned to rooms the guest is able to filter the rooms/resources based on those room features.
Note, this filtering only works when the rooms list is set to the "classic" view.
Also note that Resource features can also be added in the administrator area if you have a set of features that you consider common to most properties.
Clicking on the Edit icon, you can then edit an existing room feature. Alternatively clicking on the New button you can add a new room feature. Once you've created one or more room features, you can then assign them to individual rooms. Then, in the booking form your guests can filter out rooms based on those features until they find one that they like.
Room/resource features icons can be uploaded using the Media Centre feature.
This feature is added by the Resource Features plugin and it will only be visible if the plugin is installed by the site admin.