THCA flower is just regular cannabis that hasn’t been heated yet. It has high levels of THCA, the raw form of THC. When you smoke or vape it, the heat turns the THCA into THC, which is what gets you high. For example, if you light up a strain with 28% THCA, the heat will convert that into 28% THC, and that’s what gets you high. It’s basically the same as regular weed, just not “activated” until you heat it up.