The Metadats Lists are used to select values from a closed list. An example of metadata list could be Countries, where we can have a list of countries to be seleted from a Select metadata field:
In this section you will learn how to create new metadata lists and how to add values to the existing ones.
To access to the Custom Metadata section, go to Administration >> Custom Metadata
Search by text
Start typing a text and click Enter. The system will show you the results matching with your query
Click on this button to create a new metadata list.
This will open the metadata form, where you must introduce (at least) the mandatory fields.
Name. Name of the metadata list
To cancel the operation, click "Cancel". To save the changes and keep in the creation form, click "Save". To save the changes and go back to the previous list, click "Save & Go Back".
Once a Metadata List is created, you can also create the list of values related to the metadata list. For more information go to List Values
to clear the value and remove the filter.
or descending 
icon; 
You cannot edit the name of a system metadata list.
You can manage the list of values of the metadata list. For more information go to 
icon
to delete the selected users, or 
to cancel the operation.
If the element you want to delete has dependences , it won't be deleted and the system will show you a list of existing dependences
to go to the previous page or 
to go to the next page