Constant panty shots, bouncing breasts and dubious camera angles are hallmarks of an Ecchi title. These titles are usually sexualized and designed to titillate, depicting perverted themes and focusing heavily on the female body. Nosebleeds, suspicious hand positions, faceplanting into bosoms, expressive and exaggerated body parts and other tropes characterize this genre.
Mecha are self-propelling machines that are modeled after humans; some can change into multiple, non-humanoid formats as well. They're usually controlled by an internal pilot or by remote, but are sometimes sentient beings that move autonomously. A mecha's size ranges from bulky, wearable armor to a massive, towering contraption and beyond. While mecha have a wide range of applications, such as making manual labor easier, they are most commonly portrayed as heavily-armed war machines.
Yaoi, known as Boys' Love or BL in Japan, is a genre mostly written by women, for women, that depicts homosexual relationships between men. Japan typically uses this single category for all forms of these relationships, sexual or not. In the West, the term Shounen-ai categorizes stories that focus on the emotional aspects of the relationships, while Yaoi categorizes more of the sexual aspects and explicit content. As Anime-Planet's audience is mostly based in the West, we use the Western definition for both Yaoi and Shounen-ai.