What does 5.1 mean at Netflix?

If you want to select a language, some 5.1 appear in brackets. What does that mean?

Audio quality.

That the sound is available in 5.1. So surround sound.

I don't have a Netflix, but I would say that means there's surround sound (5 + 1 channels).

That is better sound. But you need more than just 2 boxes:-). When shooting around, the balls come from the boxes in the back and "fly" to the boxes in front.

Number of sound channels. 5 speakers plus 1 woofer