It takes a year to a year and a half of college-level classes to lay down the prerequisite groundwork: calculus through differential equations, chemistry, physics, basic electric circuit analysis. It takes about half a semester of semiconductor device theory to understand the processes in bulk silicon and PN junctions, leading up to the bipolar transistor.
When you have all that, what you have in a bipolar transistor (NPN or PNP) are sort of like two diodes connected in series, polarity opposing. The base terminal of the transistor is the common point. In an NPN transistor, the base is P-type material, and is hence the "anode" of both of the diodes.
For amplifying action, the Emitter-Base diode must be forward-biased. This means that, in an NPN transistor, Vb > Ve. For amplifying action, the Collector-Base diode must be reverse biased. This means that, in an NPN transistor, Vc > Vb. The rest is design.