"At the store", or ATS, refers to a troll named Alex that peruses the Yahoo! Answers forums appearing to be at the store every waking moment of his life. He generally likes to reside in the
religion and spirituality section and seems to either anger or make 100s of
people happy every day. Many others have been inspired and took on the same exact statement and deviated with it, or made up their own catchphrase that they relentlessly post on any forum or image board they want. Nowadays
people use, "I'm at the store", to refer to something boring in a forum or irrelevant.