Difference between plasma membrane and cell wall:
Plasma membrane and cell wall is not similar thing. Plasma membrane, also termed as cell membrane, is the outer membrane general to all living cells and it is made up of a phospholipid bilayer, embedded proteins and a few appended carbohydrates.
Since cell membranes are fragile, in some kinds of cells there are even outer structures which support and defend the membrane, similar to the cellulose wall of plant cells and the chitin wall of few fungi cells. Most bacteria too present an outer cell wall made up of peptidoglycans and some other organic substances.