M:N relationship is known as many to many relationship.
There is a many-to-many relationship when numerous data in a table are connected to duplicate entries from another table.The multiple-to-many relation is typically a duplicate of the true-life association between entities represented by the two or more tables.
A Relation is a kind of fractal dimension corresponding to the partnership between two entities.
A and B where A may comprise a case of a parent and therefore there are numerous children in B, and opposite of that also occur.