The vent is the passageway that carries the combustion gasses out. The vent connector is the pipe running from the furnace to the vent. They are essentially the same thing when the same venting material is run all the way from the furnace to the vent cap.

It may be difficult to tell the difference between Type L and Type B vents because they are made from similar components, but the vent type should be clearly printed on the vent. Both are double-walled, although Type L vents generally have a stainless steel inner wall, while Type B vents do not

Seal the gap between the flue and metal flashing with a high-temperature caulk. Warning: Do not use spray foam for any of the joints near a vent pipe. Always use fire-resistant caulking. Now, you must form an insulation dam to prevent insulation from contacting the flue pipe.