Config Backup: creates a zip file with your configuration settings
Config + Graphs Backup: adds the data used to generate the statistical graphs (roughly +15MB)
Full Backup: adds on top of all that the replay / heatmap data
Depending on the amount of historic replay / heatmap data you have, a Full Backup can take a signficant amount of time and result in a very large archive to be downloaded. If you want to limit the data retained on disk, you can use MAX_GLOBE_HISTORY=365 in the environment variables on the expert page to only retain a year of data, this setting will not impact graph data.