The level being shown on the scoreboard can be looked into by typing /level or /lvl. The /exp command is the xp level you have above your hotbar, completely different thing. The one you're viewing on the scoreboard is your total server level throughout all. You can level it up by just simply playing the game. Anything gives xp for it, even afking. Grinding mobs(skeletons preferred) is a major way to level up and is what most high-level people do to get such high levels. You could view top-level people throughout the whole server by typing /lvl top (page #). Within leveling up with that you also get points which can be used with /perks. Most perks are for grinding or pvping, some find them useful, others may not. Plus, every 50 levels you gain a half heart extra and do more damage.
