What just happened? Amazon is getting serious about its grocery delivery business. On Tuesday, the Seattle-based company eliminated the $14.99 per month fee for its Amazon Fresh grocery delivery service, instead making it a free perk for Amazon Prime subscribers.

Stephenie Landry, VP of Grocery Delivery for Amazon, said grocery delivery is one of the fastest growing businesses at Amazon, adding that they think this will be one of the most-loved Prime benefits.

In addition to doing away with the monthly fee, Amazon has also boosted delivery speed with one- and two-hour options in most cities that offer Amazon Fresh.

Due to the expected popularity of the service, Amazon said Prime members that live in one of more than 2,000 cities and towns where grocery delivery is available will need to request an invitation to shop Amazon Fresh or Whole Foods Market delivery. Those who currently use grocery delivery can continue to enjoy the service as usual.

Amazon's latest move is no doubt in response to increased competition in the grocery delivery space.

Last month, Walmart announced it would be expanding its Delivery Unlimited grocery delivery membership to 1,400 stores this fall. Walmart's service carries a monthly fee of $12.95 (or $98 for a year) and affords unlimited Walmart Grocery Delivery orders. Unlike some of its rivals, Walmart doesn't impose an upcharge on the individual cost of items - you'll pay the same price as you would in-store.

Masthead credit: Amazon Fresh by Andriy Blokhin