It's all about the CB1 receptors in your brain responsible for getting you high. While everyone talks about THC, there is little to none in fresh cannabis. Instead there's THCa which is the acidic version and will not do too much for a buzz. It has an extra molecular grouping called a carboxy group consisting of an extra CO2 molecule. That extra molecule prevents the THCa from fitting into the CB1 receptor. In order to get stoned that CO2 needs to be removed which is usually done with heat. You get high from smoking/vaping it because the heat immediately releases that grouping and then hits the resultant THC will easily attach to the receptors.
However, that is not the case for ingesting cannabis. Since the THCa will not fit on the receptor it has to be converted to THC by losing that carboxyl group, which is usually done with heat. The commonly accepted way is by using the oven set at 240°F for 40 minutes. I have run lab tests for different times and temps and have determined this to be the least cumbersome. There are other various ways to decarb both before and after extraction that will work as well. Once the material is decarbed then you can ingest it with excellent results.