The whole purpose of a fence or wall is to place a barrier or obstacle between your property and the rest of the world. Whether it is there to keep your pets in, or a security fence to keep the world out, the purpose will dictate what kind of fence you use. If it is purely for function and form isn’t a consideration then the choices are fairly simple to make. If you want it to look a good and add to the look of the property rather than detract from it, then you need to give things a lot more thought.
Deciding what you wish the fence or wall to achieve is the first step. If you have pets then of course, it needs to be able to contain them and offer sufficient peace of mind you won’t spend every moment away from the property worrying if the dog just got out and is off terrorizing the neighbourhood. Some pets are great diggers and can burrow under a fence in no time. Others, like cats, are good climbers and it would need to be a pretty high fence indeed to deter the average feline.