Hi Trishla,
The Reference Selector is intended to select an attribute of an associated (*:1 or 1:1) entity of the object in your data view.
The Reference Set Selector is intended to select an attribute of an associated (*:*) entity of the object in your data view.
The Input Reference Set Selector is intended to select an attribute of an associated (*:*) entity of the object in your data view. It creates a popup page for you to select multiple relations.
See the documentation links Srilatha posted.
Go Make It
Hi,
Check out the following :
Reference Selector : https://docs.mendix.com/refguide/reference-selector/
Reference Set Selector : https://docs.mendix.com/refguide/reference-set-selector/
Input Reference Set Selector : https://docs.mendix.com/refguide/input-reference-set-selector/