In the most simplest form Heos is basically Denon’s answer to Multiroom(multi zones) Sound System in the form of a  free mobile app for the ultimate control.

HEOS is supported by Denon and Marantz product brands and it  works through the home Wi-Fi network. Whether it's a single HEOS speaker or a full blown home cinema system, with supported products, Heos helps you control each with ease.

HEOS supports uncompressed WAV, ALAC, FLAC Music files up to 24 bit /192-kHz. After the initial setup of the HEOS app , you can stream music to compatible HEOS devices using WiFi not depending on the location or position of the speakers, It can also stream music to a HEOS enabled receiver which in turn can play it onto the connected speakers. 

HEOS Specialities

Hi-Res Audio Support

HEOS doesn't cut corners when it comes to quality sound. To deliver the clearest audio wirelessly, HEOS supports uncompressed WAV, ALAC, FLAC music files up to 24-bit/192-kHz.

Clear Stereo Sound

When listening to two speakers at the same time, every note and lyric should be synchronized — no delays, no echo. HEOS speakers have audiophile grade synchronization to ensure your music is nothing short of excellent.

Reliable Wi-Fi & Bluetooth

HEOS connects to your home's Wi-Fi network and uses dual-band Wi-Fi to give you the most reliable, consistent connection possible. For even more convenience, anyone can play music from a Bluetooth-enabled device.

Free HEOS App

Access and manage your music from your smartphone or tablet with the HEOS mobile app (available for iOS, Android, and Amazon Kindle Fire). Plus, create profiles and customize settings for everyone in the house.

Rooms

  • Set up speakers and name each room
  • Choose the room(s) where you want to play music
  • Group rooms together with simple drag-and-drop functionality
  • Use pinch gestures to group rooms for party mode

Music

  • Access and play music from streaming services like Pandora, TIDAL, Deezer, and Spotify
  • Connect via Bluetooth to your phone or tablet to play music from your smart devices
  • Listen to tracks directly from a USB connection

Now Playing

  • View currently playing songs
  • Adjust the volume, play or pause your music 
  • Create and edit playlists for easy access to your favorite songs
  • Set up a song queue and let friends and family be the DJ

Sources

https://www.worldwidestereo.com/
https://www.whathifi.com/
https://www.lifewire.com/
https://support.denon.com/