As the video notes, MDMA works mainly by flooding the brain with serotonin. This is the same neurotransmitter that's released in higher levels when you eat rewarding foods (e.g., chocolate) and during exercise (but not when you're in love, sadly). It's obviously known to be associated with a pretty good feeling. And, the drug's effects usually last anywhere from three to eight hours, according to the video. Despite being illegal, MDMA's gaining popularity, and there's also an increased focus on research on the drug as a therapy option.
Of course, it's not all fun and amazing bass that you can totally feel. There are reports that the drug can cause a sort of hangover effect in the week after it's taken. During this period, many people feel mild to severe levels of depression.
It's important to note that one of AsapSCIENCE's cited sources is this 2002 paper. Originally, this research suggested that recreational doses of MDMA caused severe long-term damage to dopamine neurons. But, this study was infamously retracted when the researchers realized they had gotten their bottles of substances mixed up. That doesn't mean that MDMA can't cause lasting damage — it's just not quite the way these researchers envisioned. Instead of messing with the dopamine system, it can actually damage the serotonin system its high tinkers with. The studies showing this result, though, reflected doses that may not be representative of average use.
In any case, it's good to know what parts of your brain a drug might manipulate — before you get too far with any of those weekend plans.