Hi, I´ve been playing for some time now in Rm New player lobby and last night I played my first match on RM/DM medieval Siege. However I dont fully understand how ranking works. My current rank in New Player lobby is about 1300 but when I enter medieval siege lobby the ranking changes and becomes 1600 and it also displays many game modes and diferent rankings. Can someone help me please to understand how this works. Thanks!!!

Here you are: https://www.voobly.com/pages/view/65/Rating-System

your beginner rating is still shown in the medieval siege lobby. if you reach 1400 rating in new player lobby, you cant play there anymore. in medieval siege the standard ladder is Rm - Team Games and Rm- 1v1 (for 1v1 games obviously). those ladders arent capped like NPL, so it goes from ~500-2700+, allowing a more accurate rating.
DM - TG and DM -1v1 are for a different game mode: Deathmatch.
RM- intermediate can be ignored. age of chivalry is a gamemod i believe, havent seen that being played in a while though. and no idea what balance ladder is supposed to be.

in the custom scenario lobby the ladders are for the different maps/map types.