Since I've been asked these questions a lot, I thought to write some journals about it. This is from an Adopter's point of view.
What are adoptables?
Adoptables are "characters" that you can purchase for your personal use. They can be animals, humans, objects... Anything and everything can be turned into an adoptable.
What exactly *is* it that I'm adopting?
You're adopting the *character* itself, not the design, not the art, just the character.
Take this adoptable:
Art = The drawing itself = Right remains to the artist
Original Species = The lines = Right remains to the artist, unless the species is for adoption too (Not valid in case of existing species such as wolves, cats, etc....)
Design = Black coat/Golden wings/Pattern on Tail = Right remains to the artist
Character = (Original Species + Design) = This is yours
You are basically adopting the right to use the character as a whole, species + design/pattern. Usually, artists are able to do a lot of different designs so it is unlikely that that *exact* design will be recycled with another species. Orange fur with black stripes on a dog can be used again on a horse, but they are still different *characters*.
Why should I adopt one?
There are lots of reasons to adopt a character. Because you want a fursona, because you want a pet for your OC, because you like the way they look... Anyone has a different motivation for wanting an adoptable.
Where do I find them?
You can either browse dA by searching for 'adoptables' or you can go to an adoptables group. There are a lot of groups, so you might want to look at more than just one, to increase your chances to find the perfect character for you.
How do I adopt an adoptable?
First of all, you need to know that almost all adoptables have a 'first come, first serve' rule. Meaning that the first one to offer the artist what they ask, becomes the owner.
This being said, there are four main ways to purchase an adoptable:
Since they're free and you get them with little effort but be there at the right moment and place, they're the first to go. Your best bet in getting one of this kind is by watching the artist who does them.
Draw to Adopt
a) With reservation = You were the first to ask for the adoptable, so you only need to submit a drawing of the adoptable and you're done
b) Without reservation = It's like a small contest, everyone submits their drawing and the artist chooses the one they like best
You'll be asked to draw something (one of the artist's OCs or a design of your own) in exchange for the adoptable.
Not much to say here, points are dA's currency and cash is real money. There's usually a time limit to send the payment to the artist.
And always, always remember to read the artist comments and follow their rules. You might find that some are more lenient than others and will bend the rules a bit, others stick to what they have written and there's no way to change their mind. To avoid upsetting the artist and creating useless drama, please read the rules. Asking never hurts, but if they've clearly stated that what you want is *not* going to happen, please don't push.
Adoptables Journals Series:
Adoptables, Basics for Adopters
Adoptables, Basics for Adoptables Artists
Adoptables, Writing an Artist's Description
Adoptables, Design Tutorial
Adoptables, Buying Adoptables
Original Species Tutorial
Adoptables, Original Species Confusion
Adoptables, I sold one, now what?