[ (required, open tag);

type (required, more info about types accepted);

: field-name (required, native fields, and meta are supported);

: subfield-key (optional and multiple, if the field is Array or Object);

| ID (optional, int, if omitted will use the current post ID);

| filter (optional and multiple, you can manipulate results with PHP and WordPress functions);

? fallback-text (optional, shown if the field value is empty or null);

] (required, close tag).