So, I've compiled a list of different kinds of collars and leashes below with explanations of their functions and what kinds dogs they may be best suited for. Hopefully this will be helpful to those of you who aren't sure what to use when taking your dog out for a walk.
Standard flat collars
This is probably the most commonly used and most often seen type of dog collar. However, it's important to make sure to use the size that is closest to the size of your dog's neck, then adjust it accordingly. Most flat collars like these are designed to be easily adjustable to make them a few inches wider or narrower. I like to keep such collars wide enough so I can snugly fit a finger underneath. This is enough space to prevent choking the dog, but not enough so that it is so loose that it could easily slip off the dog's head.
These collars are great for big dogs such as Labradors, as their necks are strong enough that these types of collars won't hurt them, and experienced dog owners have better control as a quick tug lets the dog know which direction you want to lead them in.
This is what I prefer to use with my French Bulldog. Dogs such as Frenchies and English Bulls have wide chests that make them much easier to restrain with harnesses rather than standard collars. Canines with short snouts may also already have respiratory issues, and standard collars can easily cut off their airflow or choke them further.
I personally prefer to use harnesses designed with a wide stretch of fabric that comfortably wraps around the dog's torso, instead of harnesses that are designed with a series of straps, since I feel like this cuts into the dog's body, which could be rather uncomfortable for them.
Leader or head collars
Leader collars, also known as head collars, are a lot like slip leads in the way they keep unruly dogs from going to out of control. Part of the leash is designed to fit around the dog's face so that you have more control over the movement of his had. Whenever the dog starts to get rowdy by jumping, pulling or barking, a gentle tug will remind him who's boss. Just don't yank on it too hard, or you risk hurting or scaring the dog.
As this kind of leash is designed to loop around a dog's face, it really only works on dog's with long snouts, and not flat-faced dogs like Pugs.
Slip leads or choke chains
Slip leads or choke chains are usually used on large dogs that are a bit unrulier and like to pull on the leash whenever they go for a walk.
Slip leads are simply leashes that are looped around a dog's neck and pulled through a ring on one end of the lead so that when a dog starts to charge forward, the leash tightens around his neck, creating an uncomfortable experience that usually deters the dog from continuing to barrel on forward.
When used correctly, this is generally quite effective in keeping dogs in line, but the key phrase is "when used correctly." Owners should not rely on creating pain or discomfort to get their dogs to behave. Such collars should only be used by experienced dog owners to help teach their pets what correct behavior should be, eventually rendering the use of such collars to be unnecessary.
Prong or pinch collars
Prong collars, also known as pinch collars, are designed with blunt prongs lining the inside of the collar, so that when a dog becomes unruly, they pinch the loose skin around a dog's neck. It is important that dogs are correctly fitted for these types of collars to prevent using one that could accidentally pinch their trachea.
Again, prong collars should only be used by experienced dog owners who know what their doing, and who are using it to help teach their dogs how to behave. Don't rely on the discomfort or pain aspect to train a dog. Rather, use it as an aid to encourage correct behavior, and eventually phase out the use of the collar. If you're not confident on how to use one, don't use it.
Standard 6-foot leashes
A sturdy 6-foot leash is what I recommend all dog owners use. They give you just the right amount of control over the dog and allow you to properly lead your pet.
I am aware of how popular extendable/retractable leashes are, but I don't like them. I think allowing the leash to extend further than six feet defeats the purpose of keeping a dog on one to begin with, and is actually rather dangerous, as even the most well-behaved dogs can be unpredictable when unexpected circumstances arise.
Furthermore, there have been cases where dogs were injured when owners have accidentally dropped the end of such leashes as they were retracting, which meant the plastic handle would go flying toward their pets, no doubt terrifying the dog. In some instances, dogs have been accidentally struck in the head by a retracting leash.
The purpose of keeping a dog on a leash is for the owner to lead the pet, and not the other way around. In my opinion, a well-constructed 6-foot lead is the way to go.