difference between many to many and has and belongs to many association and explain polymorphic association

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Many to many vs has and belongs to many association, and explanation of polymorphic association.

Many to many association involves a join table to connect two models with a many-to-many relationship.
Has and belongs to many association is a simpler version of many to many, where the join table is hidden.
Polymorphic association allows a model to belong to more than one other model, using a single association.
Example: Many to many - Students and Courses, HABTM - Users and Roles, Polymorphic - Comments can belong to Posts or Videos.