There is a bunch of fields on Metadata tab, you are correct. These out-of-the-box fields can be used to store this data. However, it's not always the case. How these fields are used for presentation is heavily dependant on how developers implemented this feature. For example, Kentico can store "Page description" but it will be up to a developer how to embed this information into a page head element.
The approach will also be different depending on the Kentico version you are using and Portal Engine or MVC. Could you provide this information?