-c  indicates that target image must be compressed (qcow format only)

-h  with or without a command shows help and lists the supported formats

-p  display progress bar (convert and rebase commands only)

-S size
    indicates the consecutive number of bytes that must contain only zeros for qemu-img to create a
    sparse image during conversion. This value is rounded down to the nearest 512 bytes. You may use the
    common size suffixes like "k" for kilobytes.

Parameters to snapshot subcommand:

snapshot
    is the name of the snapshot to create, apply or delete

-a  applies a snapshot (revert disk to saved state)

-c  creates a snapshot

-d  deletes a snapshot

-l  lists all snapshots in the given image