Bishōnen (美少年, also transliterated bishounen), is a Japanese term literally meaning "beautiful youth (boy)". The equivalent English concept is "pretty boy".
The term describes an aesthetic that can be found in disparate areas in Asia: a young man whose beauty (and sexual appeal) transcends the boundary of gender or sexual orientation.
Bishōnen are usually drawn delicately, with long limbs, silky or flowing hair, and slender eyes with long eyelashes that can sometimes extend beyond the face. The character's "sex appeal" is highlighted through introducing the character by using an "eroticized" full page spread.
Bishōnen characters are fairly common in manga and anime; a heavy number of male characters show subtle signs of the bishōnen style, such as slender eyes or a feminine face.
There also exists an older variant: ''biseinen'', who have the same pseudo androgynous beauty, but are older than the "shonen" category (that is, older than 18).