What is a heat register?
Heat Register is the same thing as a floor register. The difference is that with the "heat register" one is only referring to the winter heating control aspect of the floor register.
What is a wall register?
Wall Register is practically identical to the floor register. The difference between them is very minor and is usually detectable by the presence of two screw holes on the wall register which are absent on the floor register. The holes are filled with the accompanying matching screws to be able to attach the register to the wall or the ceiling.
What is a baseboard register?
Baseboard register is a register that is used to cover the air duct in a place where regular floor registers and wall registers are unable to. That place is usually located at the corners like the one between the wall and the floor. When an air duct is that close to the corner, standard sized floor register cannot be placed there and the baseboard register is used. Baseboard register does not have a damper box, thus one is unable to control the air flow through that particular air duct. In that regard it is similar to a cold air return.
What is a cold air return?
Cold Air Return is similar to the floor register but lacks the damper box that controls the air flow on a wall register. It is just a grille that covers the opening and is usually placed on the ventilation duct for air in-take.
What is a vent cover?
Vent Cover is a general term that refers to both floor registers and cold air returns. Vent covers are simply meant to be put on any air vent opening without any reference to specific functions of that cover. If you are looking for something more explicit than just a way to close the opening in your ventilation system, then you should not use this term as to avoid confusion.
What is an air grille?
Air Grille Return or Return Air Grille is exactly the same as Cold Air Return. Although cold air return is considered to be a correct term.
What is an air vent?
Air vent is a term identical to vent cover.
What is an air grate?
Grate is also a term that is identical in use to a vent cover. Although unlike "vent cover" or "air vent" it does not limit the context to floor registers, cold air returns, or ventilation systems.