edits a user's cron table -- hence the name -- by running an editor. The actual tables for each user are kept in /etc/cron/tabs but are not meant to be edited directly.
The tables are in this format:
#min hour dayofmonth monthofyear dayofweek command 0 12 14 2 * fsck -y
Time values can be set to * (for all) or * divided -- e.g., */5 in the first field means "every five minutes"
-u username edit username table -e edit table (or create empty one if none exists) -r remove table -l list the current table