Every 12 hours, raid charges are reset. You get 3 charges each time meaning you can complete 3 raids every 12 hours. Raids can be done with 1-5 people. If you have more than 3 people, the legendary chance is increased significantly.
When you first start a raid, you must pick either easy or hard mode. Easy mode has level 60 Pokemon, but no legendary boss chance. Hard mode has level 100 Pokemon and a legendary boss chance.
There are 3 waves and a final boss battle in raids. If you defeat the boss, you get a chance to catch it!
All raid bosses have 3 31 IVs or more. You also get random items, PokeDollars, or Battle Points for completing raids.
Completing a raid is one of the best ways to get legendary Pokemon!