why is my phone stuck on the samsung logo?

[AC Question]

My phone was completely on ,so I started downloading something on my phone for an i-phone emoji app {updated}. After that I think it gave my phone a virus. My phone sent me an message, it said my phone was shown a threat by an app, and it told me to get rid of it, I had to restart my pone. so I restarted my phone and now it is stuck on the samsung logo.

 

[B. Diddy]

Welcome to Android Central! Which phone?