GADM

GADM, the Database of Global Administrative Areas, is a high-resolutiondatabase of country administrative areas, with a goal of "all countries, at all levels, at any time period." Although it is a public database, GADM has a higher spatial resolution than other free databases, and also higher than commercial software such as ArcGIS. Those sources are commonly use to complete data analysis with data visualisation such as data plots, choropleth map, etc.