Answer:
Protestants perceive Communion as (1) keeping the commandment of Christ as given at the Last Supper (3) proclaiming his death until he comes again and (3) reminding us of his continuing presence with us and our need for him.
These are present in the Roman Catholic perception as I understand it (speaking from a Protestant perspective) but in addition to this they add the belief that the bread and wine miraculously change into the essence of the body and blood of Jesus. In an extreme sense then, when a Christian receives the bread and wine they are receiving and consuming Christ, in the Roman Catholic understanding. (This depends upon a philosophic understanding of the distinction between the appearance of a object and the object's essence, which is a much longer discussion).