Front groups are deliberately misleading organizations that hide their funding, true reason for existence, and are generally controlled by another group for a political end they wish to keep hidden. You know the type, they call themselves “Greens For Saving Wildlife” but are really the Strip Mining Association of America. That kind of thing. But of course many of them are way less obvious than that.
Frontgroups.org explains their characteristics and lists many such groups that they are currently scrutinizing.