I don't know if there is a glossary for idiots but the system is just a sort of hierarchy that helps people to make some sort of sense of what looks like chaos.
If you think of a set of Russian dolls, plants can be classfied into smaller and smaller groups which each fit within each other.
Generally, gardening books only use the genus,the species and the cultivar names.
The Genus is a big group. All plants within that group share certain characteristics. Within the genus Rosa you can find both roses, apples and hawthorns. When you think about a rose hip, a crab apple and a hawthorn berry you can see a similarity. The same with a dog rose flower, apple blossom and may blossom.
The Species is a smaller group within the Genus, which allows people to see the differences between things within the Genus. So Hawthorn is the Crategeus species within the Rosa genus whereas the Apple is the Malus species within the Rosa genus.You can see similarities between an apple blossom and a dog rose and a hawthorn blossom but they are clearly different. The species name shows the difference but the genus shows the similarity.
The Subspecies, Variety or Cultivar are smaller divisions within the species. Subspecies are natural, variety and cultivar are man-made differences.