The difference between a coldframe and unheated greenhouse?

I'm really confused by this  What is the difference between an unheated greenhouse and a coldframe?  I have bought one of those four tier mini 'greenhouses' with a plastic cover to have at home so I can keep an eye on my plant babies. I don't have room for a 'proper' glass one.  We don't really have the room (or the funds) for a greenhouse at the lottie at the moment. I could build a coldframe, for home or lottie, no problem but do I need to? Help!

Thanks for explaining the difference! I did buy the mini green house for hardening off plants (veg and flowers) rather than long term crops.  So looks like it will do the job.
We treated ourselves to a large walk in netted tunnel this year which is why a greenhouse will have to wait! 
After having to go out at 1.30 in the morning to retrieve the mini green house from the other side of the garden I sort of buried the bottom of it and anchored it down by putting two long broom handles on either side of the frame at the very back and whacking them down really well.  I then cable tied the frame to the handles.  Seems to have done the trick so far.  It's been a bit windy here (again) and its made no attempt to take off yet! Cheers!

Thanks Beetroot Queen.  We have all the bits and bobs for a coldframe.  My OH is a mild mannered insurance underwriter by day and a ninja skip diver by night! Who knew  :blink:! I just can't get my head round starting some stuff indoors, some out in cold frame, greenhouse whatever.  Then doing the hokey cokey with some things but not others (in/out/in/out) at night!  Gah! Its bringing out my OCD tendencies for everything to be just so  . I must breath and relax!

On top of all the other comments made I also use the cold frame to start of some seeds such as lettuce, brassicas and leeks etc as well as hardening off plants. I do this because even in an unheated greenhouse the temperature gets too warm during the day.