Air fryer/ pressure cooker / dehydrator questions

[HareOverThere]

Please can someone explain in a basic way what the difference between an air fryer, pressure cooker, dehydrator, slow cooker is?
Would you use all of them or do they do the same things?
Which one is most useful?
Is it worth paying the extra for one of the £200 type ones or do the £50 ones do the job as well?
Am looking for something I could cook meat, potatoes, veg, chips etc in without having to use the oven.
Thankyou!

I have 3 out of 4.
AF - does great, healthy chips in a minimum of oil, but also acts as a small oven & can roast/bake small quantities of most foods.
PC - very quick to cook, e.g. dried chickpeas in 15 mins instead of 80, oxtail stew in 30 instead of 2-3 hours.
SC - very gentle heat, cooks slowly & can be left on for many hours.
D - can't think why I would want to remove moisture from food?

I've just bought the instant pot Pro crisp and I'm quite impressed so far. A casserole cooks in a fraction of the time, I've currently got steaks in the sous vide and the air fryer does lovely chips! I had a pressure cooker years ago and used it a lot, so I expect this will be similar. I have a fancy electric oven that does everything too, but my main motivation was to save energy costs.
My mother had a cheap air fryer which she said was rubbish, which put me off for a while, but I'm glad I've bought this.

I've got an air fryer with these shelves and a rotisserie, cost £50 on a black Friday deal. My rented house doesn't have e working oven so I bought this. I live alone but it's family size. No pre heat needed, superfast. I've cooked my Christmas dinner in it. Usually cook jacket spuds, roasted veg, chips, fish, pizza, kebabs, fritatta, cakes, biscuits etc. I can even hard boil eggs. I love it! Much cheaper than putting an oven on for one person cooks quicker versatile, easy clean.

The only one I haven't got is a pressure cooker, the rest I use regularly.

I use our airfryer a lot for everything from roast potatoes and chips to sausages, chicken and fish. It's worth the £90 I paid for it.

We're gardeners and often have gluts of certain veg and fruit which are great dehydrated and then used in sauces etc. Ours also helps with lessening food waste so if mushrooms are a bit past it, we dehydrate them, store in an airtight box for ages, really intensifies the flavour. Fruit is dried and used in winter fruit salad or granola/muesli.

Slow cooker is used for casseroles, stews, pulled pork/beef and for cooking the meat for Sunday dinner (except chicken).

Honestly they're so useful!