What, exactly, is it supposed to mean? What is the difference between "track" and "trace"? Any difference is a subtle one. "Track" means: to follow a trail, usually with the intention of finding where it leads, and "trace" means (according to the dictionary) to track, to follow step by step, to detect, to discover the whereabouts of.
So the UK government want to test people and then find where they've been before finding out where they are. Except they know where they are because they tested them and must have contact details in order to send the results.
Meanwhile the Welsh Government have the more reassuring slogan of: "Test, Trace, Protect". Now this makes sense. You test people, you trace their contacts and you protect everyone by getting them to self-isolate. Scotland likewise has a "Test, trace, isolate, support" strategy.
Why are the different? Well, it may be that when the Welsh Government tried to translate "Test, track, trace" into Welsh they realised that it would be "Profi, olrhain, olrhain", which is just stupid. Because Welsh doesn't have as many words as English, words tend to have slightly broader meaning, so you don't have so many synonyms. Besides, testing and tracking is only the start. The important part comes when you've tracked any contacts and you act to stop them spreading the disease further.
Of course "Test, track and trace" is just another of the Tory's meaningless three word slogans, like "Brexit means Brexit" and "Get Brexit Done". It sounds good until you start to think about what it actually means...
Anyway, to change the subject, I actually got out for a short walk yesterday. Living in lockdown is not that different to normal life for us, but it is different enough that it's making me feel tired and lethargic -- though that could also be the hay fever. I was trying out a step counter app that I downloaded for a very specific purpose. There is a health app with pedometer that came already on the phone, but you can't reset the count to zero, which is something I need for a project I want to do this week. More about that in due course.