Good question. The answer is it is different things to different people. From what I have read there are 3 main types of bed rest (don’t forget I am not a doctor):
1. Hospital bed rest
This is the strictest of all the bed rest options. It would mean you literally don’t get out of bed at all and have everything done for you, in hospital (obviously).
2. Home bed rest
This is mid level bed rest which involves lying in bed/on the couch and only getting up to go to the shower or toilet. People on this type of bed rest tend to have meals pre-made and everything at their fingertips to minimise the amount of time on their feet. I may put myself on home bed rest for July and August (22-30 weeks).
3. Modified bed rest
This is what I am doing at the moment. It is very much about doing what you are comfortable with. For me, I limit the amount of time on my feet and only pop to the shop 50m away. I will go to the cinema or for dinner or to visit a friend but only if I can be dropped door to door so no walking is required. I try to lie down rather than sit down where possible. I don’t do any exercise either.