In order to sustain peace, stability, and comfort in the society and to establish control over the people, the Community stripped the population off of all emotions, sensations, color, pleasure, pain, and suffering and built the society based on the concept of Sameness.
The Receiver of Memory is chosen to essentially bear all of humanity's past memories, so that the people won't experience any pain or discomfort and can live peacefully, with no stress or worries in their minds. The Committee of Elders (the leaders of the Community) are extremely careful when it comes to choosing the next Receiver of Memory, because it is one of the most important jobs in the Community.
Aside from being in charge of all of the people's past memories, emotions, and experiences, the Receiver of Memory is also the Giver's successor, and he or she is given the task to advise the Committee of Elders when they need to make an important decision about the future of the Community, as the Receiver possesses all of the knowledge of the past.
This is why it's difficult to choose the next Receiver and why the job requires several key qualifications; thus, in order to be the next Receiver of Memory, one must show intelligence, courage, integrity, wisdom, and the capacity to see beyond. The chosen Receiver of Memory in the book is Jonas.