Anime/manga aimed at young girls, or anime/manga containing abundant themes and content that would appeal to young girls.
That Card Captor Sakura anime is shoujo
Anime or Manga meant to break your heart, filled with love triangles, betrayals, and darkness. Filled with bishounen, and required by japanese law to have at least one shounen-ai relationship in the series.
Despite being male, I read a good deal of shoujo manga because of the interesting angst-filled plotlines.