WinRAR can create an archive consisting of several files. Such archive is called multivolume and individual files composing this archive are known as volumes. Generally volumes are used to store large data amounts on removable disks or transfer data by email.
WinRAR can create RAR and ZIP volumes. Another name, widely used for ZIP volumes, is ZIP split files.
By default RAR volumes have names like 'volname.partNNN.rar', where NNN is the volume number. For RAR 4.x archive format using -vn switch it is possible to select another, extension based naming scheme, where the first volume file in a multi-volume set has the extension .rar, following volumes are numbered from .r00 to .r99. RAR 5.0 archives do not support -vn and extension based names.
RAR volumes can also be solid and self-extracting. First self-extracting volume has a different (i.e. not .rar) file extension, for example, .exe for Windows SFX volumes.
To unpack RAR volumes you need to start extraction from the first volume. If volumes are stored on non-removable media like a hard disk, you need to put all volumes in the same folder before starting extraction.
ZIP volumes have names like 'volname.zip', 'volname.z01', 'volname.z02'. Use a volume with ".zip" file extension in all archive processing operations like starting extraction or opening an archive.
Unlike RAR volumes, ZIP volumes cannot be self-extracting. WinRAR needs to have access to all ZIP volumes of multivolume file set at the same time, when creating or unpacking them. So it is impossible to create or unpack ZIP volumes on removable disks, one volume per disk. You need to create them all in the same folder and then you may copy them manually to removable disks if you need it. Similarly, you need to collect all ZIP volumes in the same folder before starting extraction.
It is impossible to add, update or delete files in already existing volumes. You can create only a new volume set.
Starting from version 3.40, WinRAR stores the volume number inside of RAR volumes. You can see this number at the top of "Show information" dialog if you apply Show information command to volume. This number may be useful if original volume names are lost and you need to restore correct names manually.