@anggunthequoh hallu, boo!
I think I'm just as baffled as you when I first heard about it sparking controversies online. When I hadn't gathered much, I thought it was true even. However, just like the many being debunked, Semibisexuality was exposed to be merely invented by people indulging in affixing a label to describe the slightest variation in their sexuality (No pun intended). It is unbacked by legitimate knowledge from the adepts, which goes without saying it lambasts bisexuality much less the most and only acceptable identification for this sexual orientation that is, "Heteroflexibility."
Anyhow, despite being verified to be made-up, it still has been explained to be the sexual orientation of someone who is "more" attracted to the other gender and "less" to their own. Suppose I'm a semibisexual, I fall for more than one sex/gender not necessarily at the same degree as would bisexuals, saved for one detail: I'm a semibisexual "with a preference for men." It's as though I'm straight but "periodically" take fancy to someone of "my" sex/gender.
P.s. I am absolutely prepared to be wrong about how I understood and explained what Semibisexuality really is, so have at it, once you gathered more and found I missed/wronged some points.