ESI is a term defined by lawyers meaning Electronically Stored Information. It is an intentionally broad term designed to encompass any electronic information, stored anywhere, by any means, by any technology that exists now or in invented in the future that might be relevant to a case. It could be on a desktop computer, laptop, tablet, smartphone, cellphone, server, external storage device, digital camera, camcorder, “cloud” storage, web-based email service, or somewhere else. It is a term that is not used by computer professionals, but with a slight bit of explanation they will get it.  Look for my post on communicating with computer people if you want to understand this part even more. All ESI is potentially discoverable.  The best work from the legal side is being done a group known as the Sedona Conference.  They are trying very hard to figure out how electronic discover fits in to the legal world and their work is well respected.  I am no lawyer, but I see alot of articles about judges’ decisions on e-discovery and forensics where the judge or winning side cites the arguments and procedures defined by the Conference.