Boris Johnson has confirmed the system of track and trace in England will start on Thursday.
If you test positive for the coronavirus then you will be asked to provide details of who you have come into close contact with.
You will be told you must self-isolate for 14 days, even if you never become sick.
The prime minister said if people did not, then the government would consider bringing in fines.
The point is to pivot from lockdown for everyone to isolation for a few.