Income Protection is a policy designed to pay a monthly benefit to you to support you if you cannot work because you are ill or injured. They do not typically include cover for redundancy (however, there are other types of policies that can look at this).
It pays a percentage of your gross salary (or take-home pay). There are short term policies, also known as budget Income Protection, and long term policies, also known as full Income Protection.
Income Protection is there to support you in your time of need however it is not designed to make your financial position better if you are not able to work. There are restrictions in place on how much cover you can have.
Amount of cover available
Policy end age (which can often be dependent upon occupation)
Reviewable or guaranteed premiums
Additional benefits, if any
Criteria to claim against (also often dependent upon occupation)
Treatment of existing conditions and effect on their premiums
Deferment periods (depending upon your current sick pay arrangements from your employer)