This video is about the simple structure of plant cell walls and their functions.
The cell wall is composed of three layers. Outer to the inner side are
The Middle lamella
Primary cell wall
Secondary cell wall
And occasionally Tertiary cell wall.

Composition of cell wall
Middle lamella
Mainly made up of calcium and magnesium pectate.
Primary cell wall
Made up of 3% cellulose and 50% hemicellulose. Glycoproteins are also present.
Secondary cell wall
The composition of it is just opposite to the primary cell wall, here hemicellulose is 5 to 25% and 50 to 95% of cellulose is present.
Other components like xylan, lignin, etc are there.
Due to this more cellulose, this layer becomes rigid and nonelastic.
Mainly found in collenchyma, sclerenchyma, and xylem vessels.
Tertiary cell wall
Purely cellulosic in nature. Xylan is present in this layer.

The function of the cell wall

1. It gives structural integrity to the plant cells and also protects them from mechanical damage.
2. Helps to stand erect, by providing mechanical support.
3. It allows protoplasmic continuation by plasmodesmata. Which is important for the transport of substances.
4. Prevents any osmotic bursting of cells.
5. Helps in cell-to-cell adhesion and prevents the entry of undesirable molecules.
6. Acts as protective covering barriers against pathogens.