True surround sound means speakers are positioned around you. Some soundbars on this list, like the Samsung Q990C also come with a subwoofer and two smaller rear channel speakers, meaning you can place them around your room.
However, other devices with only one soundbar claim to offer surround sound. What this means is they deliver a stereo effect, which seems more like sound is coming from different directions, but isn't.
Many of the high-end soundbars in this list also have Dolby Atmos built-in. Again, this isn't technically surround sound, but the audio tech is advanced and creates the illusion of immersive sound by bouncing sounds off the walls and ceiling around you.