I will carefully explain what the published astrometric Gaia data for any given star mean in detail, and how they can be used in practice. In particular, I will elaborate on the precision estimates and on the quality/reliability flags given for each star in the Gaia data releases. In addition, I will give a preview of the forthcoming epoch astrometry data, i.e. of the individual astrometric measurements for all Gaia sources, to be published for the first time in Gaia DR4 in early 2026. Since Gaia mainly does one-dimensional measurements, the structure and usage of these epoch data are not intuitive for an astronomer.