DALnet's nick registration service allows users to register a nickname by providing a password, preventing other users from using it. NickServ registration is required for such things as registering channels and sending/receiving memos.
The SENDPASS command will allow a user to request that his or her nickname password be sent to the email address on file for that nickname. This command should not be relied on as an alternative to managing your own passwords, but only as a "backup" in case of extreme situations. Please remember that you are still responsible for remembering your password(s) and keeping them private. Do not share your password(s) with anyone.