This item is a reward from the World of Warcraft Trading Card Game.
The picnic allows you to summon a beach umbrella and hibachi grill that lasts for 3 minutes. Any player can click on the grill for Grilled Picnic Treats.
Picnic Basket also can be found listed on the Black Market Auction House.
Here you can buy Picnic Basket for EU or US Servers.
Also you'll get guide for receiving Picnic Basket
Additional budget for Character transfer or Character boost to max level. BMAH Services in Shadowlands now requirement to have a max level character on server, so Trial character will not work.
Free time on evening, if you choose selfplay option