What is Append and Append To Privilege in Dynamics CRM 365?

When there is N:1 or 1:N relationship between two entities then one entity will be lookup to another entity.

So, when we try to set the value of Lookup field then here these two records are getting linked. To set the lookup value of such relationship entities record then we need Append & AppendTo privilege.

An example: EntityA is having relationship with another EntityB as 1:N. Here lookup field will be created on 'N' side of Entity i.e. lookup field of EntityA will be created on EntityB form. It will look like below.

Now to set the lookup value of EntityA field on EntityB form then we need Append & AppendTo privilege.

Append: In this situation, Dynamics user(s) must have Append privilege on EntityB. It will allow user(s) to associate related entities record on this EntityB.

AppendTo: Dynamics User(s) should must have AppendTo privilege on Entity EntityA. It will allow EntityA records to get Filled/Set in the lookup field on the form of Entity EntityB where user already have Append privilege assigned.

You can watch the demo of Append & AppendTo privilege.