Since we don't have much to go on, they could be anyone from adventurers to spies. Maybe they are characters who have been wronged in some way and form the alliance for revenge, or perhaps they are idealists aiming for a greater good but have to keep their actions secret.
Well, without more context, it's hard to say exactly. It might be a story that delves into the behind - the - scenes happenings of a secret alliance. For example, it could show how the members of the alliance met, what their initial goals were, and how they keep their alliance a secret from others. It could also involve some sort of conflict or challenge that they face as a secret group.
No, they're not exactly the same. Webtoons can come from various countries and have different styles and themes. Manhwa specifically refers to Korean comics.
Webtoons can be seen as comics. They tell stories visually, have characters and plots like traditional comics, but they might have different ways of scrolling or panel arrangements for online viewing.