Complex Meta Fields
Simple meta field can have only one basic field type. Custom meta field can contain one or more basic field types. This allows you to create more complex fields, like the address for instance. Custom meta field can be set as required or to use the repeater, and each basic type inside the field can also be repeated.
There is no limit in combining the basic meta fields in a single custom field, the only limitation is what individual basic meta fields are imposing (like use of repeaters or required flags).
Using drag and drop, or move buttons, you can change the arrangement of basic field types inside the custom meta field.
Custom Meta Fields can’t be used in the Legacy Metaboxes.