Of course you can cook them from raw .A casserole for example .Just chuck it all in .Meat ,veg ,stock ,etc Stir it round ,switch it on and walk away
I sometimes put a ham hock in it and let it cook on slow overnight .let it cool,cut the meat off ,shove that back in the pot with stock ,dried soup mix and loads of chopped winter veg and a good handful of parsley .When it's nearly time to dish up bung some dumplings on the top for the last 30 mins .You can let that cook all day and just need to do the dumplings .
I buy a large joint of beef .I put in the pot ,switch it on and get on with my life .It makes it own gravy .You don't have to keep hanging over the oven basting it .
That's why it's called a slow cooker :))
Have never heard of a make called just " Crockpot" .They are mainly well known brand names like Morphy Richards etc.
Crockpot is a generic term for a slow cooker .The Americans call it a crockpot .