Hello :) Example ; if you say '' What is this? '' = '' Bu nedir? '' → ''this'' is BU in here. If you say '' I am eating this. '' = '' Ben bunu yiyorum. '' → ''this'' is BUNU in here. If you say '' What is the color of this? '' = '' Bunun rengi nedir? '' → ''this'' is BUNUN in here. I HOPE I HELP YOU :)

"Bu" means "this", but "bunu" is the accusative form (ie. it receives the action). "Bunun" means "of this" - it's probably a good idea to learn "bunun" as part of a phrase instead of an individual word.