If you have a party in mind, how would you go about inviting people? Text blasting? Calling your acquaintances? E-mail? Or through the power of social media like Facebook or Twitter? Or even through the power of word-of-mouth?
The point is that you need to get your message across a certain group effectively or your party will be a huge flop.
In a similar sense, if you own a business and would want to get people to attend a certain event, you would need the right method to reach your target audience. In this case, b2b event telemarketing may be the key to your problems.