Power Query is the Data Transformation engine which can be used in many applications, and Power Query Editor is the Graphical User Interface(GUI). It uses M Query (M Language) to Transform the Data.
(Link for Previous Video - https://www.youtube.com/watch?v=b_n88HV93Hg)
M meant for "Mashup", as M Language, Mashup the data from many data sources and creates final outcome by transforming using the Code. M Language is a functional language. It has a rich library of functions thru which it gets the results and allows us to transform the Data. We can even create our own functions, which will be discussed in my upcoming Videos.
(Link for Previous Video - https://www.youtube.com/watch?v=b_n88HV93Hg)