Teleseminars are telephone seminars or what most folks refer to as conference calls.  By far, most of us have attended one (or hundreds) some time in our life.  Webinars are seminars held on the internet.  Unfortunately, people use both terms interchangeably so it can get pretty confusing.  However, there are some distinct differences -- and advantages to both -- you'll want to consider for your next conference:

Teleseminar

PROS - It is easy to do and super accessible to almost everyone due to the low cost of phone service these days.  It's low cost because it requires minimal equipment/service:

• Telephone and headset - smart idea, unless you want a constant crick in your neck and a redhot ear
  
• Analog phone line (the kind you get from your local phone company) - I don't recommend either a cell phone or IP phone service like Vonage (even though I've been a customer for five years) due to poorer call quality and likelihood of having a connection problem.
  
• Conferencing service - there's plenty of cheap or even free (check out www.FreeConferenceCall.com) services that not only will let you conduct the call with dozens of folks participating, but will provide a recording of the call immediately after you're done.  You can use the recording as an added benefit to the participants, transcribe and create a product, use it for your marketing purposes, etc.
  

Webinar

PROS - You have full audio / visual capabilities, which can be a huge attraction especially if your participants need to see what you're talking about.  The range of visual possibilities is "ginormous" (as my daughter Haley would say) including PowerPoint / Keynote presentations, video, sharing your desktop, viewing online resources, webcam, etc.  Many webinar services like www.InstantTeleseminar.com provide pre- and post-call webpages where your attendees may download resources, hear a personal message from you greeting / thanking them, listen to the call later and be given a special offer.  During the call, they may post questions for you; some more advanced services will even allow them to "raise their hand" to ask a question or comment to other participants about a particular point you just made.  Also, you may see how many folks are on the call at any one time and even the location from where they are calling.

CONS - Webinars can be pretty complex.  For example, you may:

• be distracted by constantly monitoring the number of participants on the webinar.
  
• need to remember to start the recording, stop the recording, and extend the recording time if your call goes long.
• end up with a lot of customer service complaints during the actual webinar.  There may be call clarity issues (they can't here you or your guest clearly), technical glitches with video, computer problems, etc.
  
• have would-be participants not attend since they need to be in front of a computer to gain access to a webinar.  It's smart to use a service that also provides a regular call-in number as an option for them to at least be able to listen if internet isn't convenient.
  
• a co-leader or moderator on the call, they can help you manage the flow of questions / comments.