ESO Plus is the paid subscription option for Elder Scrolls Online: Tamriel Unlimited.

ESO Plus is an option because ESO is a buy-to-play game and does not require any subscription. ESO Plus is supposed to be like a VIP program which provides subscribers with rewards for each month that they are subscribed. Players on both PC and consoles will be able to subscribe to ESO Plus.

ESO Plus currently costs $15 USD per month and will bestow the following rewards.
CROWN ALLOTMENT
When you are subscribed to ESO Plus you will receive 1,500 Crowns every month. This amount of Crowns is the same amount that you could have purchased with the $15 that you are spending on your ESO Plus subscription.

You can spend Crowns in the Crown Store which sells items like costumes, motifs, potions, food, mounts and more. In the future it is likely that experience potions or boosters will be sold on the Crown Store as well.

DLC ACCESS
When you are subscribed to ESO Plus you will be able to access any and all available paid DLC (downloadable content), or expansion packs. At the moment no such DLC exists.

In the future things like new zones (Wrothgar and Orsinium) and quests might be paid DLC. If you are not subscribed to ESO Plus then you will have to buy these expansions at a fixed cost per DLC. We don’t know the price of future DLC at this time but anywhere from $20 to $60 is expected for a new zone.

If you are end your ESO Plus subscription then you will lose access to all of the DLC that you have not purchased separately.

10% BONUS
For each month that you are subscribed to ESO Plus all of your characters will receive the following bonuses.
Gain 10% additional experience from all activities.
Gain 10% extra gold from monster and enemy drops.
Gain 10% additional experience, or inspiration, from crafting.
Your trait research timers are reduced by 10%.