Fields page aggregates all the data fields (measure or grouping) which are used to create this visual. These fields are displayed in the fields panel of Visualization pane in Power BI.
Following properties of each field is changed individually by selecting each of them:
- Display Name - user friendly name of the field
- Description - description of this field. It will be displayed as tooltip in Power BI.
- Allow - describe that the field should accept a measure or grouping or any of them in Power BI.
- Allowed Data Type - data type of the field accepted in Power BI.
To know more about them, consult Power BI capabilities documentation.