There's a Men's and Women's division in both Street and Park.
Street League is currently the path for Street. The path for Park as of March 28, 2019 has not been announced yet.
All of these sanctioned events earn you points towards the rankings. On that rankings list, countries and regions get a certain allocation of spots in the Games.
From the USA Skateboarding organization:
Skateboarders will have the opportunity to qualify for the Olympics based on their three best results in World Skate sanctioned events during the 2019 qualifying season (now through September 15, 2019) combined with their six best results during the 2020 qualifying season (September 16, 2019 – May 31, 2020). The 2020 World Championships will also be a direct qualifier for the games for the top 3 podium spots at each event.
Generally, it's performance enhancing drugs that are the focus, not your typical street drugs, although those of course can get you in trouble, too. Find out what's prohibited here.
WADA (World Anti-Doping Agency) sets the standards and other agencies do the testing and reporting. You can get randomly tested at anytime, even outside of a competition.
The International Olympic Committee has recognized World Skate as the governing body running it.