Ferrets are domestic animals, cousins of weasels, skunks and otters.
(Other relatives include minks, ermines, stoats, badgers, black-footed
ferrets, polecats, and fishers.)  They are not rodents; taxonomically
they're in between cats and dogs, a little closer to dogs.  They are
friendly and make excellent pets.  If you've never met one before, the
easiest way to think of them is somewhere between cats and dogs in
personality, but rather smaller.  They can only see reasonably well,
but they have excellent senses of hearing and smell.  Some are cuddly,
others more independent; they vary a lot, just like other pets.

Ferrets are a lot of fun.  They are very playful, with each other and
with you, and they don't lose much of that playfulness as they get
older.  A ferret -- or better, two or more [4.3] -- can be a very
entertaining companion.  They are smarter than cats and dogs, or at
least they act it.  They are also very inquisitive and remarkably
determined, which is part of their charm but can also be a bit of a
bother.  They are friendly, and they do know and love you, though for
some of them it can take a year or so to fully bond.

They can be trained to use a litter box [7.2] and to do tricks [8.2],
and most of them love to go places with you, riding on a shoulder or
in a bag [8.8]. They sleep a lot, and they don't particularly mind
staying in small places (a cage [5.4], for instance, or a shoulder
 bag) temporarily, although they need to run around and play for at
least a couple of hours a day.  A "single" ferret won't be terribly
lonely, although the fun of watching two or three playing together is
easily worth the small extra trouble [4.3].  Barring accidents,
ferrets typically live 6-10 years.

Ferrets have lots of good points as pets, but there are some negatives
as well.  Like kittens and puppies, they require a lot of care and
training at first.  They're "higher maintenance" than cats; they'll
take more of your time and attention.  Ferrets have their own distinct
scent [3.7], which bothers some people, and many of them aren't quite
as good about litter pans [7.2] as cats are.  Although most ferrets
get along reasonably well with cats and dogs, it's not guaranteed, so
if you have large, aggressive pets (particularly dogs of breeds
commonly used for hunting), keep that in mind.  Likewise, small
children and ferrets are both very excitable, and the combination
might be too much [3.8].

Finally, the importance of ferretproofing must be emphasized.  Ferrets
are less destructive than cats, but they love to get into EVERYTHING,
so if you keep them loose you'll need to make sure they can't hurt
themselves or your possessions [5.1]. They love to steal small (and
not so small!) objects and stash them under chairs and behind
furniture.  They like to chew on spongy, springy things, which must be
kept out of reach or they'll swallow bits.  Accessible boxes, bags,
and trash cans will be crawled in, and houseplants within reach are
liable to lose all their dirt to joyful digging [5.2].  Finally, many
ferrets tend to scratch and dig at the carpet [5.2].  Naturally, these
traits vary from one ferret to another, but they're all pretty common.
If you're not willing to take the necessary time to protect your
property and your pet, a ferret may not be for you.