I dabble more than a little in the legal world, but that's OK, because the legal world dabbles quite heavily in the world of technology. Nowadays, metadata is the smoking gun in court, and e-discovery is the ballistics test that uncovers it.
The concept of e-discovery, or electronic discovery is simple: it is the discovery, identification, and production of electronically stored information (ESI). However, the execution can be involved, complex, and frequently contentious.
Take for example something seemingly simple and benign: the keyword search. If you and I want to find out about something online, we open up Google or Bing and type in some words, such as "e-discovery keyword search". We typically get back a ton of links, in order of relevancy. We pick and choose from among the links to find what we need. Rarely do we have to go beyond the first few pages to get the information or resources we're looking for.