This is Meta Repeater plugin. Its used to create dynamic meta fields for post and custom post types.
The Repeater Fields for Gravity Forms allow you to create one or more sets of fields that can be repeated.
The Repeater Fields for Contact Form 7 allow you to create one or more sets of fields that can be repeated.
The Repeater Fields for WPForms allow you to create one or more sets of fields that can be repeated.
The Repeater Fields for Elementor Forms allow you to create one or more sets of fields that can be repeated.