Here is a great video that covers the growth and progress of digital modes and the through the current explosion of the new FT8 mode! This guy explains things very well and is very informative. I follow him on YouTube and I suggest you do also. He also explains the development of modes from Joe Taylor K1JT and how Taylor has changed the ham radio world!
FT8 is the newest weak-signal mode from Joe Taylor, K1JT, and friends. It operates very much like JT65 but is four times faster and more automated. Learn a little about the history of digital modes and conversational vs bare essential modes! Two sample QSOs!