Many-to-many relationships

 Suppose users can belong to many teams and teams can contain many users.

users
teams
team_user

User model:

public function teams()
{
    return $this->belongsToMany(Team::class);
}

Team model:

public function users()
{
    return $this->belongsToMany(User::class);
}

Usage:

$user->teams;

Attach:

$user->teams()->attach($teamId);

Detach:

$user->teams()->detach($teamId);

Sync:

$user->teams()->sync([1, 2, 3]);

Scenario

This is common for:

Users ↔ Roles
Students ↔ Courses
Products ↔ Categories
Posts ↔ Tags