Oxford University scientists report that only 8.2% of human DNA is likely to be doing something important, i.e., is functional. This number is quite different from one given in 2012, when a number of researchers involved in the ENCODE (Encyclopedia of DNA Elements) project stated that 80% of our genome has some biochemical function.
The rest of the human genome, the non-8.2%, is leftover evolutionary material, parts of the genome that have undergone losses or gains in the DNA code, often called "junk" DNA.