From www.wizards.com
Updated July 30th, 2015
Constructed decks must contain a minimum of sixty cards. There is no maximum deck size; however, you must be able to shuffle your deck with no assistance. If a player wishes to use a sideboard, it must contain exactly fifteen cards.
With the exception of basic land cards, a player's combined deck and sideboard may not contain more than four of any individual card, counted by its English card title equivalent. All cards named {Plains}, {Island}, {Swamp}, {Mountain}, and {Forest} are basic.
The following card sets are permitted in Standard tournaments:
Theros
Born of the Gods
Journey Into Nyx
Magic 2015
Khans of Tarkir
Fate Reforged
Dragons Of Tarkir
Magic Origins
On October 2nd, Battle for Zendikar will be released. Theros block and M15 will rotate out.
There are no cards banned in Standard tournaments.