What is this New Digital thing/TV starting in August 2016?

Sir/Ma'am 4-6-16 I'm not understanding why we have to change to digital TV. First of all, this is PROBABLY going to cost me more each month. What is wrong with the box I have now? I have a box where I can watch my own movies I have in my collection. I don't want that to disappear. I have a DVD/VHS player that I need this present box for. I'M not willing to give this up and not watch my OWN PERSONAL movies. I have a 4742HDC box by CISCO So, what happens to this issue? Bill.