How do you understand the weakness chart in Pokemon Pokédex and learnset?

Question

So, I know there is a provided Pokemon Pokédex and learnset that gives out the stats, weakness of Pokemon and other things. But I don’t know what the weakness mean. Like for darkrai, it has 0 for psychic, nothing for ice, 2 for bug, 1/2 for dark and darkrai has other weaknesses with nothing, 1/2 and 2. I just want to know what nothing, 0, 1/2 and 2 means in the weakness chart. Thank you!

Answer 1

the numbers are the multipliers. darkrai as your example, dark has a immunity to psychic attacks, thus the damage is multuplied by 0. if it says 1/2, the damage is mulitplied by .5. 2 is multiplied by 2. dual types gain a new level of weakness and resistances. 1/4 is mulitplied my .25 and 4 by 4. hope I helped.
edit: oh yeah, and the nothing just means it neither resists or is weak to that type of attack, thus iys multiplier is 1.