You might know that inside your body there are different organs. A cell has the same thing going on.
Scientists use the word organelle to describe a cell's different parts.
When you examine the ER you should know that you will find two different types. Rough and smooth ER are also different shapes. The rough is like sheets of cloth while smooth are slightly tubular. The purpose of the ER is to collect proteins. The vesicle is formed when the ER pinches off a part of its membrane.