Loop biopsy

So I went for my pre op yesterday and they said when I go for my biopsy next Wednesday under General anaesthetic  (there was a large area covered in abnormal cells) that it would be a loop biopsy. During my colposcopy the gyne said that my smear queried cgin he said it had picked up cells which are quite far up and it was rare to be found on a smear. He wanted to do a small biopsy (Cone I think, he drew a picture and said if he went for a large one it wouldn't be very good with me being 25) however then saw 90% of mg cervix covered in cells too so decided for GA. Why would I have a loop biopsy and not a cone one with the high cells? Sorry I don't really understand it all and daren't google! Xx