The 2 primary long distance services are direct dial long distance (1+/outbound) where you pick up the phone and dial 1+area code+number, and toll-free (1-800/inbound) where someone calls you on a toll-free number by dialing 1-800-Your number.  In addition to 800, other valid toll-free NPAs (first 3 digits) are 888, 877, 866 and soon to be 855.

There are 2 types of long distance transport.  Switched and dedicated.

Switched long distance

Switched long distance is your basic old long distance service.  In a 1+ call, you pick up the phone, dial your long distance number and the call is then transported to your long distance carrier through your local phone company/phone line.  This is the origination leg of the call.  The call arrives at the long distance carrier's switch and it opens another call to the person you were calling.  This is the termination leg.  This termination leg begins at the long distance carrier's switch, travels to the local phone company of the person you are calling and ends up at the final destination, the person you called.  These two call legs are tied together and you're talking.

In a toll-free call, the process is basically reversed.  Someone dials your toll-free number, it travels through the local phone company that is servicing the phone they are calling from, arrives at the long distance carrier and then terminates to your local phone line, through your local phone company.

The term "switched" comes from your call traveling through the local phone company's switch and being routed to/from the long distance company's switch.

Dedicated long distance

With dedicated long distance your office is essentially on the long distance company's network.  A dedicated circuit is established between your phone equipment in your office, and the long distance carrier network.  There is essentially only one leg in a dedicated call, which is why the per-minute rate is much lower.  Because you are on the network, there is no need for the call to travel through the local phone company switch.  The last leg of the call travels directly to/from the long distance switch, to/from your phone equipment.  The only per-minute costs are associated with the leg that is not on the network.  In the case of a 1+ call from your office, the call travels from your equipment directly to the long distance carrier's switch through the dedicated circuit.  The call is then terminated in the same fashion as as the switched example above.  With a toll-free call, the call is originated in the same manner as the switched example above,  then arrives at the long distance carrier's switch and is terminated directly to your equipment through the dedicated circuit.

Of course there is a cost associated with the dedicated circuit.  Your local phone company supplies the transport from your building to the long distance carrier's network.  This is called the local loop and the monthly charge is based on miles and capacity.  The closer you are to a local phone company POP (Point of Presence) , the cheaper the loop.  Your local phone company went to great expense to lay all that cable in the ground and of course they charge for it.  A loop can run anywhere from $100 to $1000.  Generally, metropolitan areas are full of local POPs and you will likely get out for a $100-$200.  Because of the variables, each loop has to be quoted as every one is different.

Because of the cost associated with the loop, it's easy to see that a dedicated scenario is suited for larger volume.  A detailed analysis of your existing usage and expenditures will determine exactly what the effect would be.  Also keeping in mind that you'll likely be able to get rid of many of your local phone lines.  We will provide this analysis at no charge.  Generally, you would need at least 10-15 simultaneous calls running at a given time (1+ and 800 together) and about 100,000 minutes of usage for it to make a significant dent in your bill.  Or, from another point of view, if you're spending $2,000 or more per month, a dedicated solution is worth looking at.