What apps are hidden apps?

I'm curious, what exactly do you mean by "hidden apps" when it comes to cryptocurrency and finance? Are you referring to apps that are designed to be discreet or inconspicuous in their use, perhaps for privacy reasons? Or could it be apps that are difficult to find in mainstream app stores, maybe due to regulatory restrictions or other factors? I'd like to gain a clearer understanding of what you're asking before providing a more detailed answer.