No, they're not the same. Manga are typically professional and commercially published works, while doujin are often created by fans and may be based on existing manga or other properties.
Doujinshi (Doujinshi, anime, game, etc.) refers to a manga, novel, anime, or other re-created work based on a well-known anime, novel, game, etc. It is usually created by fans or re-creation enthusiasts who love the work and has nothing to do with the original work.
Doujinshi manga would usually be adapted to a certain extent from the original work, adding original plot, characters, re-composition, style, and other elements to make it different from the original work. As the basis of their creation came from the original work, Doujin manga often had the same or similar storyline and character settings as the original work.
Doujinshi manga was very popular among fans of the original work and could attract some viewers who were new to the work. At the same time, due to the flexibility of Doujin manga, there were many different types of Doujin works such as horror, fantasy, science fiction, and so on.
The reaction of site.com to manga can vary greatly. It could be highly supportive, promoting and featuring manga prominently. Or it could have a more limited engagement, only showcasing selected titles. It all depends on their business strategy and target audience.
I wouldn't recommend looking for unblocked manga sites as they often violate copyright laws and can be risky. It's better to use legal and authorized platforms to enjoy manga.