Part of my gums has descended and revealed my tooth root painlessly?

Ok: Not sure what your question is. This may have been caused by periodontal issues, bruxism, or even vigorous brushing. Without an exam or even your age it is impossible to tell. For that reason you should seek the help of a local dentist.

Recession: Sounds like you have recession of gum tissues over a lower tooth with resultant root exposure. Lots of possible reasons, including gum infection, tooth positioned outside of proper bones housing, parafunctional habit, overly aggressive brushing, and many other reasons. Please see your Dentist for appropriate care.