This question is incomplete. Here's the complete question.
Read The Giver, by Lois Lowry.
Why do you think the community made the distinction between “selection" for Receiver of Memory and "Assignment" for all other occupations?
Answer: Because he got selected, he didn´t get assigned to it.
Step-by-step explanation:
In this novel, all people are assigned a job when they become adult members of the community.
However, at the Ceremony of Twelve, Jonas discovers that he has been assigned as the new Receiver of Memory, and the Chief Elder explains that, contrary to the rest, he has been carefully selected for that task by the Elders after following a strict selection process.