Moe is a Japanese word for something that produces feelings of affection. In short, ‘cute’. A kitten, small child, or a painting may be described as moe. It can also refer to fashion (think J-pop stars or idols), characters, art-styles, or stories.

There is a theory that moe was introduced by post-WW2 Japanese artists to distance themselves from the hyper-nationalistic imagery of Imperial Japan. In any case, Osamu Tezuka showed that dark and complex stories can be told without a dark and complicated art-style, leading to a number of Japanese works - even ones aimed at an older audience - using a moe artstyle.

There is definitely a subculture that fetishises moe, but I’ll leave it at that.