What is ‘junk DNA’?

I heard about junk DNA, but how can be possible to have junk DNA. Wasn’t supposed that all our DNA to be useful?



In genetics, ‘junk DNA’ is a term used to describe the regions of the DNA that are noncoding. DNA contains instructions used to create proteins in the cell. However, the amount of DNA within a cell is vast thus not all of the genetic sequences present within a DNA molecule code for proteins.