# ACF - Reference Types
Reference types help easily build cross-reference between Shopify objects by allowing users to select one or multiple handles based on type of reference field.
There are 6 reference types in ACF. All value produced by ACF is either in string (non-repeatable field) or JSON string (repeatable field).
- When attribute “Allow selection of multiple values” is checked, each value will be separated by |, for example: hello|world|2020, book|shoes|pen|eraser.
- Product, Collection fields can be edited in Editor tab via Shopify resource picker.
- Page, Blog, Article, Linklist fields can be edited in Editor tab via selection field editor.
- In case you don’t see item you want to select, press “load more…” button.