BESM is a table top RPG system.
It is like Dungeons & Dragons, but let's say more of an anime equivalent. It usually uses 2 D6 (two die with 6 sides)
The GM (similar to a DM) creates a story / world and each player can create whatever type of character they want (granted that the GM will allow it)..based off of a point system where characters start with X amount of points. In the system me and my friends use we start off with around 250 points, each character has 3 main stats (Body, Mind, and Soul). To put points into those main stats it's 10 point for 1 level in Body / Mind / Soul. The scale is 1-10 1 being equivalent of weakest in universe 10 being the strongest in universe. You also have attributes (essentially powers/abilities), skills, and defects. Defects allow you to have a defect to your character that gives you extra points.
I'll give you an example of what a character is :
My character in the current BESM game I'm in is an Elven Vampire whom uses shadow magic.
He has a 7 Body 4 Mind and 5 Soul
His attributes include : Level 1 Super Strength, Level 2 Massive Damage, Level 4 Weapon (claws), Fast taken 3 times, Level 4 Power flux, Level 2 Heightened sense, etc.
His skills include : Level 4 Occult, Level 2 Wilderness Tracking, Level 2 Urban tracking, Level 2 Wilderness Survival, Level 3 Languages (he knows 3 languages... computers, elven, and magic)
One awesome moment in my friend's game that was pretty funny...
We are interrogating guards who are made out of shadow and have cloaks on so you can't see what they look like.. I ask him 3 questions... Do you know where blah is? Do you work for blah? Are you lying to me?
Each question they blatantly lied... So i ask the GM if I can I roll to detect if he's lying... He says ok roll, I end up rolling 12 (max roll you can get in 2 D6 System : Also note that rolling a 2 is an epic fail and rolling 12 is epic win)
So I essentially crit on detecting if he's lying... the GM goes ok... this is what you do..
You go up to the guard... Rip off his cloak and put your hand on their shadow form and absorb them and look at the rest of the group and say "He's lying..." Because apparently I just went up to the guy and absorbed him entire soul because he was made of shadow magic, and instantly knew all the information they had and that they were lying.. One of the people in the game starts laughing and then gets a serious face looks at my character and says in character.. "Well that escalated quickly."