Beer It Forward (BIF) is a lot like a Secret Santa exchange, only without Christmas, and with beer. Generally a group will get together when the OP posts an "NBO" (New BIF Offering) and folks sign up. Once sign ups are complete, the OP decides who each person's target is, and sends the targets' information to their respective senders. Who your target is is a secret, but the next step is a "Hints and Hauls" thread, where hints are given as to to whom you are shipping, and once beer is shipped out the hauls are posted for all to see. When everyone ships at the same time it's called a "Shotgun BIF". There is a less-used version called a "Traditional BIF" where one box makes the rounds from one person to the next, however there's a lot less excitement and it takes significantly longer. There are also BIFs based on sports betting, where the senders and targets are determined by the outcome of sporting events and/or fantasy leagues. A Lottery It Forward (LIF) is when someone offers up free beer, all you need to do is enter to win. Entering to win can take one of many forms, such as donating to a charity for raffle tickets, guessing the outcome of a sporting event, or sometimes just saying "I'm in". Beer karma dictates that generally if you win free beer, you should pay it forward and give away free beer yourself as well; there are some exceptions (for example, if you win a donation raffle, you've already done your part by donating) There are also two ongoing threads in this forum, SWTFYW and The Locals. Each of these started off as a Shotgun BIF, but the group decided to keep it going after that had concluded and keep shipping beer back and forth to each other. Since then, each thread has done multiple Shotgun BIF rounds, multiple Traditional BIF rounds, and countless LIFs, trades, and each has grown to be like a family. You are welcome to dip your toe into these two, but truthfully each has escalated to a fairly ridiculous level and I would recommend trying out a "smaller" BIF or two first.
The above post needs to be a sticky at the top of this forum. The only thing missing is what SWTFYW actually stands for. Otherwise, great explanation.
Thank you @Lazhal, very flattering. As for what SWTFYW stands for, you'll have to read the thread to find out. Tagging @blue-dream re: sticky request.