Common terms needed to understand DATASHEETS

There are several parameters which each and every component depend on. It is the sole duty of every Electronics engineer to understand his need and find a component that best suits his need

The parameters of the component are well served of in a datasheet but many times I find the datasheet to be really difficult to even understand. Specially the Short hand versions of the terms

For example in a BJT datasheet I had the following queries

1. What is VCO, VBO, VEO? Cos we never apply voltage to one of the terminals of the transistor any time and these voltage ratings are the highest of all

Is there any guide or any pic that represent these better ? Any vidoe that explains will also do

Googling just gave the same datasheet in different formats Is there any better way to google for understanding DATASHEET