What does this field?
- It allows you to select / return data from another field (radio, checkbox, select, repeater or flexible content) either from default value or from another source (post/page/user/term/option page).
- This way, you can use it to make a optimized reusable / component-like system.
What is the difference of this vs. Clone field?
- Database: Clone field will save a lot of data just like if your field merged with the targeted field / field group. This field instead just save a string (containing field slug + index + post_id) in the database and will use get_field() to return the data.
- Advanced Select: This field allows you to select: choices, layouts, rows, values.
In the admin, it will render you a select field so you can choose a specific value:
- If you target a checkbox / radio / select, it will allow you to target a specific choice.
- If you target a repeater field, it will allow you to target a specific row.
- If you target a flexible content field, it will allow you to target a specific layout.
On the front, it will return an array matching the data you selected.
You have a option page containing a group field with tons of fields inside it that is acting as a configuration for something. You want to use all this configuration multiple times for some reason, this field will allow you to target that with ACF UI and get the data with a get_field() and returning your specific data.