title: Sequelize model references vs associations
body: <p>Just starting to use Sequelize and I've setup a bunch of models and seeds, but I can't figure out references vs associations.  I don't see the use case for references if they even do what I think they do, but I couldn't find a good explanation in the docs.</p>
  
  <p>Is this redundant having references and associations?</p>
  
  <pre><code>module.exports = (sequelize, DataTypes) =&gt; {
    const UserTask = sequelize.define('UserTask',
      {
        id: {
          primaryKey: true,
          type: DataTypes.UUID,
          defaultValue: DataTypes.UUIDV4
        },
        userId: {
          type: DataTypes.UUID,
          references: { // &lt;--- is this redundant to associate
            model: 'User',
            key: 'id'
          }
        }
        // ... removed for brevity
      },
      {
        classMethods: {
          associate: models =&gt; { &lt;--- makes references redundant?
            UserTask.belongsTo(models.User, {
              onDelete: 'CASCADE',
              foreignKey: {
                fieldName: 'userId',
                allowNull: true,
                require: true
              },
              targetKey: 'id'
            });
          }
        }
      }
    );
    return UserTask;
  };
  </code></pre>