Many-to-many relationship in MS SQL for what?

Question

SQL

Dear gurus of your business, tell me, please! Explain more precisely. Gnawing granite science in the study of MS SQL, namely in T-SQL.
I understood the one-to-one connection, I also understood the one-to-many connection.
But I just don't understand the many-to-many relationship. Why is it required, why create an intermediate table, etc.
Explain in a simple way please! And some real life examples, please.
Thank you!

Answer 1

Real life example: There is a table of goods of an online store and there is a table of promotions that apply to goods. Any product can participate in multiple promotions and any promotion can include multiple products. And there is no way to store information about these relationships other than using an additional table.