It's for if you can't maintain you're weight, then you can have high calorie 'feed' overnight - it's like liquid food, kind of like milkshake is the best way to describe it! There's a choice of either passing a tube up your nose and swallowing it down your throat, which I tried when it was first suggested to me to have feeds, but couldn't swallow the tube, or you can have a small hole cut into your stomach and a permanent tube fitted, called a gastrostomy. It has an access valve that sits against your skin on the outside that you attach the feed to, and inside your stomach it's held in by a balloon filled with water, which usually pops after a few months and then you (or my mum in my case) just pull it out and fit a new tube and fill the balloon again. It's a bit of a pain as even though once the skin and muscle around the hole heals (a bit like a piercing I suppose) it still sticks out slightly so you can see it through clothes depending on what clothes you wear and I choose not to wear bikini's and stuff on the beach as I don't want people staring at me, but that's personal choice. I usually have a feed about 5 nights a week, in addition to eating normally in the daytime, but I guess it varies from person to person depending on how many calories they manage to get down them in the day.I've tried just eating enough in the daytime, but even with high cal milkshakes etc, it's not enough to sustain my weight, and even with the feeds, if I have a bad infection and lose my appetite, the feeds don't even sustain my weight and I still lose weight. That's why even if I'm a good weight for me I still feed at night, as then when I'm more sick it's not as big an impact when I lose a bit.