Token

A Token is a marker for a permanent that is not represented by a card.

Tokens don't have a casting cost. Tokens can be produced by all sorts of cards — ranging from Instant and Sorcery spells to enchantments and creatures with regarding abilities. When Tokens are send to the graveyard, to exile or a player's hand, they cease to exist.

Comprehensive Rules
110.5. Some effects put tokens onto the battlefield. A token is a marker used to represent any permanent that isn’t represented by a card.

110.5a A token is both owned and controlled by the player under whose control it entered the battlefield.

110.5b The spell or ability that creates a token may define the values of any number of characteristics for the token. This becomes the token’s “text.” The characteristic values defined this way are functionally equivalent to the characteristic values that are printed on a card; for example, they define the token’s copiable values. A token doesn’t have any characteristics not defined by the spell or ability that created it. Example: Jade Mage has the ability “{2}{G}: Create a 1/1 green Saproling creature token.” The resulting token has no mana cost, supertype, rules text, or abilities.

110.5c A spell or ability that creates a token sets both its name and its subtype. If the spell or ability doesn’t specify the name of the token, its name is the same as its subtype(s). A “Goblin Scout creature token,” for example, is named “Goblin Scout” and has the creature subtypes Goblin and Scout. Once a token is on the battlefield, changing its name doesn’t change its subtype, and vice versa.

110.5d If a spell or ability would create a token, but an effect states that a permanent with one or more of that token’s characteristics can’t enter the battlefield, the token is not created.

110.5e A token is subject to anything that affects permanents in general or that affects the token’s card type or subtype. A token isn’t a card (even if represented by a card that has a Magic back or that came from a Magic booster pack).

110.5f A token that’s in a zone other than the battlefield ceases to exist. This is a state-based action; see rule 704. (Note that if a token changes zones, applicable triggered abilities will trigger before the token ceases to exist.)

110.5g A token that has left the battlefield can’t move to another zone or come back onto the battlefield. If such a token would change zones, it remains in its current zone instead. It ceases to exist the next time state-based actions are checked; see rule 704.

Ixalan
Ixalan features 10 tokens: two faction-less tokens (Illusion, Plant) and one for each tribe (Merfolk, Vampire, Dinosaur, Pirate). Thematically matching the tribes there are four Artifact–Treasure tokens.