Maria - Not sure what context you were looking at, but to me, email list simply means the list of contacts you have for any particular purpose ... like your email list of prospects, your one for friends, etc.
The term "email list" is also used in email marketing. Your list can be opt-in from a sign up newsletter on your website or it can be rented or bought. There are ramifications for buying and renting email lists for email marketing purposes. There are whole issues around that.
Ohhhhhh. I see. It's a software program that sends email for you. So, if you sign up for a newsletter, the program (like Listserv) will send the newsletter to all of the people on the list (the recipients).