You should understand the basics within a few days. 12 players split into teams (duos or trios, depending on your choice + the odd solo). You have to get 3 clues to find the location of the boss, each clue is located in various compounds on the map, after that you have to kill the boss, take the bounty and extract... all whilst other teams are trying to do the same.
Sometimes there are multiple bosses per round. Once you have the bounty, you are granted 5 seconds of dark sight (wall hax), which allows you to see the enemy, but the enemy team can also track the bountys location via the map and using their own more limited version of dark sight. It sounds a little confusing but if you watch any Hunt Showdown basics video it will make sense.
You will play against bots and other newbies if you play for the first time, at least until you get to rank 11 at which point the bots vanish and you will only go up against other players and it will most likely get a lot harder with a lot more dying until you get to grips with the gunplay, not triggering sound traps etc
You 100% need to use heaphones though, play through speakers and you're going to have a bad time picking up all the audio cues etc