Smart IPTV App (a.k.a. SIPTV App) provides you easy access to IPTV channels. As it mentioned on their website, Smart IPTV App does not include any IPTV subscription. You should have IPTV Channels from a provider to watch in Smart IPTV App.
There are many platforms and devices that runs Smart IPTV App. Right now Android TV, Amazon Fire TV, LG Smart TVs, Samsung Smart TVs, and MAG devices are available.