What Things We Can Define In The Model?

There are lot of things you can define in models, the few are:

1. Validations (like validates_presence_of, numeracility_of, format_of etc.)
2. Relationships (like has_one, has_many, HABTM etc.)
3. Callbacks (like before_save, after_save, before_create etc.)
4. Suppose you installed a plugin say validation_group, So you can also define validation_group settings in your model
5. ROR Queries in Sql
6. Active record Associations Relationship