From the beginning, E-cigs were classified by Model Numbers. Large distributers started selling, and as a sales tactic, they started branding the e-cigs with their own names, so buyers would think they were getting something unique. This only caused confusion, and with so many e-cigs now, it's hard to keep up.
The Model Identification Guide shows the popular models, and other names they go by. Since new things are being developed daily, check the quide often for Revisions.
ESF E-cig Model Identification - Revision 5.pdf