"are records of the internet services that have been accessed by a device. They would include, for example, a record of the fact that a smartphone had accessed a particular social media website at a particular time."
and:
"ICRs do not provide a full internet browsing history. The ICRs do not reveal every web page that a person visited or any action carried out on that web page."
How this will work in practice is anyones guess at the moment - every time I think of something short of logging every packet header sent/received in the UK (which leads to a staggering amount of data needing to be logged), I think of things that would slip though (and therefore wouldn't fulfil the first statement)...
[1] https://www.gov.uk/government/uploads/system/uploads/attachm...