What is the difference between TENS and E-Stim?
Transcutaneous electrical nerve stimulation (TENS) is the use of electric current produced by a device to stimulate the nerves for therapeutic purposes.
TENS machines are designed for pain relief, they are not designed for sexual stimulation or pleasure. They tend to be less powerful and have levels of control and modes more suited to medical therapy than sexual pleasure or torment. - It is one of the reasons some have a treatment timer, that shuts everything off after 30 minutes of treatment - something you might not want just as things become interesting.
TENS machines tend to have unusual connectors which make it hard to use different electrodes.