Фан service put simply is stuff the producers do to boost rating usually in еще mature anime. The most common one is revealing a girl's undergarments in some way или form. Why is this bad many great Манга get turned into animes with to much Фан service. Фан service often can ruin an Аниме and reduce its amount of viewers. Not to mention it also lowers the chance of it ever becoming dubbed.

I will now give examples of some animes that overdid this compared to its manga.

1 rosario vampire in the Манга it is teen at most parts at least, In the Аниме they put a pantie shot almost every 3minutes which can be really annoying and ruin the epicness of the scenes.

However the worst one of my Список is girls bravo. This Аниме went beyond words of Фан service. The Манга was about 15 plus and had few душ scenes.
In the Аниме there was about 3 bath scenes with nudity per episode making it was mature.

HOPE THIS HELPED THOSE WHO DO NOT UNDERSTAND THE TERM Фан SERVICE.