Email Lists
I talk a lot on this blog about email lists, usually with the assumption that the definition is a foregone conclusion. Typically with internet marketing, this is the case. However, there is some nuance to the term. In general, an email list is a list of addresses to which the same content is sent. However, when referring to internet marketing, this definition is perhaps too broad.

Opt-In Email Lists
In marketing, there are opt-in email lists. Typically, these will include a link or some other method for assuring that the customer wants to continue receiving the offers. In many cases, list emails will include an unsubscribe button for letting the administrator know that the user is “opting out.” of a particular email list

Targeted Email Lists
There are also non-opt in lists, usually purchased in bulk for mass mailings (or email blast). Often times, these lists are a better tool for the job than opt-in lists. Curating an opt-in list is a much greater time-commitment and is usually more-suited toward newsletters and occasion offers. Purchasing an email list (or email database) in bulk is a great way to get a precompiled list of thousands of addresses ready to be contacted. In many cases, these databases are sold or leased based on region or industry, lending them much better for targeted email marketing.