The Internet community treats any type of unsolicited mass email campaign as spam. Here are a few spam related terms:

Definitions

Aquaintance Spam

Unsolicited email sent to people that had previous contact with you as a business operator: old customers, subscribers to one of your newsletters etc.

Unsolicited Bulk Email (UBE)

Any type of mass email (commercial or not) that is sent to people who didn't fill in a subscription form. How many emails are considered bulk? There's a thumb rule that says anything that overpasses dozens (over 20 or more). But it also depends on the content and purpose. Maybe you won't be considered a spammer when you send an unsolicited joke (or a link to your newly released webpage) to a list of your friends, but you can't do the same thing with people that you haven't made aquaintance with in the past.

Unsolicited Commercial Email (UCE)

Any type of email that arrives in your email box unsolicited and calls you to place an order for some product or service. Any unsolicited email that contains links towards commercial websites.

Junk Email

Apart from UBE/UCE, junk email can also be an automatically-sent message by someone's virus-infected computer that has your address in the contact list. UBE and UCE can also be considered junk email.

Spam

Every email in the previous cathegories.

How Do You Get on Spam Lists?

It is rather a simple process in which you give your email address to a known company in order to receive their weekly newsletter or any other form of email promotion, and that company gives your address to third parties without bothering to ask you.

Another case is when you publish your email address on discussion lists, forums or have your email address listed in web based (opt-in) lists. This is where email harvesting softwares interfere, automatically collecting your address and supplying it to spammers. Spammers also use softwares that generate possible email addresses using real domain names, but we'll talk about spam softwares in a subsequent section.

Ok, So What If I Spammed You?

This is not a joke! Many spammers are wining that parties who fight against them are in fact violating their freedom of expression, and possibly limitating other people's chance to benefit from their tremendous business opportunity.

At a closer look, what they do is called fraude. Why? Because they expect to increase their earnings on other people expenses. Who is paying spammers? Every person that uses Internet one way or another: ISP servers at first, but also each and every end-user that pays internet connection. Spam costs are currently estimated at $10 billion.

Call it a truism, but behind an unsolicited bulk email you will never find a competitive, client oriented company that sells quality products/services. These are entities that should't exist in the first place, and could never make it in the business field by playing straight.