This allows the contents of the field to be treated as text, changing the functionality that's available to it from numeric or date to text. This option is only displayed on fields not recognised as text natively.
Field Type
This allows you to change the field from a Metric to a Dimension or Geography, or from a Dimension to Geography. See Geography Fields for more information.
Index
This allows you to add an index to the field in order to increase read performance. Generally, indexes should be added to fields that will be used in joins or filters.
Drill To
This allows you to define a Dimension field to Drill Down to.
Format
This opens the Column Formatting menu, allowing you to apply default formatting options and apply meta data to the field.
Default Aggregation
This allows you to assign a default aggregation to be applied to the Metric field when added to reports. This can be overridden in the Report Builder.
Copy
This allows you to create a duplicate copy of the field, which can then be formatted, converted, or changed separately to the original.