It's a Screen Ratio: Most DVB/MPEG-2 boxes receive a 4:2:0 screen ratio for picture resolution, but certain DVB/MPEG-2 channels, usually network and/or studio feeds, use a 4:2:2 screen ratio.
This involves the ratio of video data to vertical pixel and horizontal pixel colour. It isn't part of the standard DVB specifications but is used mainly by studios that need better picture quality than standard DVB offers.
Most FTA receivers can't receive signals with the 4:2:2 ratio, but some can.
Contrary to belief, 4:2:2 isn't a form of Encryption.
As far as we punters are concerned, 4:2:2 is increasingly used for Sports etc. feeds and without suitable kit, part of the hobby remains unfulfilled!