It means betting that the price will go down instead of up. But to do that, you have to borrow (step 1) shares to sell (step 2); then buy them back to close out the transaction (step 3). The "borrowing" step is an extra step compared to just a normal buy low/ sell high aka "long" like what you did. I've been trading over a year and I never short- it's more complicated and risky so I have avoided it. If you want some entertainment, the movie the Big Short is based on a true story of the guy that bet against the housing market before the crash. Here's the best scene. https://www.youtube.com/watch?v=Cxjdj5_5yNM. Edit: The scene is him borrowing the shares to short of mortgage backed securities.

It means betting that the price will go down instead of up. But to do that, you have to borrow (step 1) shares to sell (step 2); then buy them back to close out the transaction (step 3). The "borrowing" step is an extra step compared to just a normal buy low/ sell high aka "long" like what you did. I've been trading over a year and I never short- it's more complicated and risky so I have avoided it. If you want some entertainment, the movie the Big Short is based on a true story of the guy that bet against the housing market before the crash. Here's the best scene. https://www.youtube.com/watch?v=Cxjdj5_5yNM.