Quarter on quarter, at an annual rate
The quarterly change compounded as if it continued for a year; the US convention for quoting GDP growth.
The United States reports GDP growth as the quarterly change raised to the fourth power, so a quarter of 0.5 % growth is reported as about 2 %. The euro area and the UK quote the plain quarterly change. The two are not comparable without conversion, which is why each region page states which is shown.