How a pump is connected to a plug and socket?

If pump is three phase, then there are three phase wires generally colored as red(R), yellow(Y) and blue(B). They are connected to a starter as they are not started directly. The starter has two terminals to be connected to supply namely phase and neutral.

Step-by-step explanation

If pump is single phase then it will have three terminals namely Line (red),  neutral (Black) and Ground (green). Generally these are the colors of the terminals. 

When we connect them to the plug then the green or ground terminal is connected to the thickest and longest conductor so that excess current get discharged to the ground and the line and neutral are connected to the remaining two conductors of the plug. They are connected to socket in same coordination i.e. line conductor to line terminal and neutral to neutral.