shadow Mapping - Depth buffer

Hi,
Now I am learning shadow mapping concept. I want to deep understand about depth buffer.

Please Explain,
1.How to calculate the depth value.
2.storage representation of depth value. Example with detail explanation.

Please Explain,
1.How to calculate the depth value.
2.storage representation of depth value. Example with detail explanation.

Please research and ask concrete questions directed at concrete problems. We’re not here for teaching.