It did 2 things really well. Measured the spectrum of the microwave background very precisely. Showed it had the blackbody spectral shape predicted by the Big Bang model. When first shown at a meeting of the American Astronomical Society it got a 2 minute tanding ovation. Made a precise map of the microwave background intensity in different directions.
Microwave background is quite uniform.
On a 0-3.6K scale you see no structures. 1E-4 See radiation from our Galaxy. Away from our Galaxy see excess noise. Universe was not perfectly smooth at early times. Seeds of Galaxy formation.