Because sun is jealous of my skin.

No.

Sunburn is a term for red and inflamed skin.

It is caused by ultraviolet radiation present in sunlight.

Sunlight consists of three types of ultraviolet radiation, UVA, UVB and UVC.

Does it contain UVZ as well?

Just listen.

Our skin is made up of cells.

These cells have DNA.

When we are in the hot sun for very long.

The UVB radiation enters into our skin cells and starts to damage the DNA.

DNA damage can lead to cancer.

Thus, to reduce the risk of cancer, the damaged skin cells kill themselves.

This programmed cell death is called apoptosis.

Apoptosis activates the immune response.

As a result, the blood flow increases to that area to heal the skin.

This leads to red and inflamed skin which we call as sunburn.