Two modes will be playable- Kick Off, and Pro Clubs.
While FIFA 18 is due out in a month and a half, you can get the chance to play it early if you get into its closed beta- and if you did, you should have received an email from EA with a code by now (handy tip, check the Spam and Promotions folder to see if it’s not hidden away in there if you can’t find that email in your inbox).
The beta will be beginning tonight at 9PM PST (or midnight on August 11 Eastern time), and will let you play two game modes- Pro Clubs, and Kick Off (meaning The Journey, Career Mode, and Ultimate Team, three of the most popular modes in the games, are all out). It should at the very least give you a good idea for how the moment to moment gameplay will be.
FIFA 18 is due out on PS4, Xbox One, Nintendo Switch, and PC, with last generation versions on Xbox 360 and PS3, on September 29.