Storing multiple select values in django

I am a fresher in Django. I was searching for a article or SO thread describing the way django stores multiselect list box values in the database but couldn't find one.

In my case I have categories list box with options for example(C1,C2,C3). The category name can be a long one. I want to assign multiple categories to single user. It can be single category assigned to a user as well.

My model will look like this(cat_name fiels depends on how it stores in the db)

class Category(models.Model):
    user = models.ForeignKey(User)
    cat_name = models.CharField(max_length=100)
    #or cat_name = models.TextField()

My question is how django will store the values in the db

id    user_id    cat_name
1     1          C1&C2&C3
2     2          C1&C2
3     3          C3

Or

id    user_id    cat_name
1     1          C1
2     1          C2
3     1          C3
4     2          C1
5     2          C2
6     3          C3

If it's the first case then I'll use TextField else CharField. & used in the first case is just an example.

Any suggestion/link is highly appreciated. Thanks in advance.