Short answers, pulled from the story.
The satellite was designed to test the universality of free fall and verify if two bodies of different composition fall at the same rate in an identical gravity field. Scientists sought precision one hundred times better than Earth-based measurements using this floating laboratory.
The mission began in April 2016 when a Soyuz rocket delivered the payload into orbit from French Guiana. Launch occurred at 21:02:13 UTC from the Guiana Space Centre outside Kourou on that date.
Scientists constructed specialized instruments containing concentric masses made from platinum-rhodium and titanium-aluminium-vanadium alloys. One unit held platinum-rhodium alloy masses while the other contained titanium-aluminium-vanadium alloy known as TA6V.
On the 4th of December 2017 the first results were released showing the principle held true within extreme precision. Published data confirmed the equivalence principle holds true within an order of magnitude better than previous Earth-based measurements.
Engineers deployed inflatable booms to increase atmospheric drag and ensure the satellite re-enters Earth's atmosphere within twenty-five years. Decommissioning was announced on the 18th of October 2018 after exhausting its supply of nitrogen fuel.