There are 4 Relationship / Associations types in CakePHP:
Relationship      Association Type                        Example
one to one         hasOne                                        A user has one profile.
one to many      hasMany                                     A user can have multiple post.
many to one      belongsTo                                   Many post belong to a user.
many to many   hasAndBelongsToMany              Post have, and belong to many tags.

CakePHP relationship types examples.

Eg: hasOne-> A user has one profile

class User extends AppModel
{
    public $hasOne = 'Profile';
}

Example: hasMany-> A user can have multiple post.

class User extends AppModel {
    public $hasMany = array(
        'Post' => array(
            'className' => 'Post',
            'conditions' => array('Post.approved' => '1'),
            'order' => 'Recipe.created DESC'
        )
    );
}

Example: belongsTo -> Many post belong to a user.
 

class Post extends AppModel {
    public $belongsTo = array(
        'User' => array(
            'className' => 'User',
        )
    );
}