Smooth Endoplasmic Reticulum (SER)
A cell is the basic unit of living organisms that is capable of reproducing itself exactly. That is, although eukaryotic cells (such as plant cells and animal cells) contain components, which are called organelles, those components do not reproduce themselves independently of the cell of which they are a part.
An endoplasmic reticulum (ER) in a cell is a system of membranes which is the site of manufacture of proteins and lipids.
The "smooth" component of the term "Smooth Endoplasmic Reticulum" or "SER" indicates that there are no ribosomes attached to the surfaces of the endoplasmic reticulum - this is as opposed to "Rough Endoplasmic Reticulum (RER)" which does have ribosomes attached to it.
See also the functions of cell organelles.