Folder recursion is the process of archiving sub-folder of the folders you have selected. Recursion depends on the archiver in use. When using single archive mode, it is recommended that all folders on the folder list are located on the same drive. Selecting folders from multiple drives may cause some of the files in the archive to be replaced by others if the same folder names are used on both drives.
Internal ZIP archiver
Recursion is always enabled. In multiple folder mode, MyZippa uses relative paths, in single archive mode, it uses absolute paths.
WinRAR with multiple archives
-r switch recommended
WinRAR with single archives
-r -ep2 switches recommended
7-Zip
-r switch required for folder recursion
WinZip with multiple archives
-rp switch recommended
WinZip with single archives
-rP switch recommended (note the capital P, which has a different meaning to the small p in -rp)