This term can mean several different things. Try to use a more specific tag:

• choke_chain - a chain collar where one end slips through a loop on the other side, allowing it to tighten around the neck when the leash is pulled. Sometimes used with breath_play.
• prong_collar - a chain collar with short prongs that point inside against the neck of the wearer. This style can be seen in both regular chain_collar or a choke_chain style collars.
• spiked_collar - a collar with spikes on the outside, often shown for decoration.
• chain_collar - a collar made out of chain

• collar - a thick band that goes around the neck, for fashion or bondage or kinky play.
• choker - a fashion necklace that fits tightly around the neck, often in the middle. Which gives a choker a distinct appearance which is different from other styles of necklaces that hang down over the chest.

• leash_pull - when a leash is being pulled on
• asphyxiation - when something makes it hard for a character to breathe.