Explain the fermentation that occurs in the bread dough?

Purchase a couple of Cookbooks for all your 'explain this or that' kitchen chemistry questions.
Enroll in a culinary program at a community College or university.

Hi. In this and the next question, I think you’re looking for a level of instruction that’s beyond the hotline.

Here are a few articles from Food52 to get you started, but I’d recommend a good basic bread book such as The Bread Baker's Apprentice to get you started.

https://food52.com/blog/9479-5-links-to-read-before-baking-bread
https://food52.com/blog/12196-josey-baker-s-10-essential-tools-for-baking-delicious-bread
https://food52.com/blog/9343-chad-robertson-on-the-next-generation-of-bread
https://food52.com/blog/9336-chad-robertson-s-starter-and-levain
https://food52.com/blog/9344-chad-robertson-s-tips-on-mixing-bread-dough
https://food52.com/blog/5607-8-ways-to-master-the-art-of-bread-baking