Thrifting refers to the act of shopping at a thrift store, flea market, garage sale, or a shop of a charitable organization, usually with the intent of finding interesting items at a low price.
A larger philosophy permeates the act of thrifting which celebrates the recycling of formerly-owned items, finding new use and new love for vintage material goods which had been thrown out, and the thrill of imagining what the former life of the item was like.
A zine called "Thrift Score", published in the 1990s by Ms. Al Hoff, celebrated this lifestyle. Many "resale" shops pull their more interesting items from thrift stores and sell them at higher prices - the premium is because the "digging for gold" has already been done.
Read more about Thrifting: Origin, Thrifters, Reasons For Thrifting