Here's a view of un-pollinated corn silk:
See how green it is?
Once the pollen laced seeds hit the silk, each strand which is attached to an individual kernel, must be pollinated to produce the mature kernel of corn. It will go from green to a burnt brown look.
Some folks will break one tassel off and brush the silk to help insure ears get pollinated. If you ever open an ear of corn and have kernels that never made, it's because the silk strands never got pollinated.