Screen your servers from unknown automated bots.
To enable this run
/setup setverify True <channel> <role>where the channel is the channel you which will be visible to users on joining. While the role is the role which will be given if the user is successfully verified.
To edit the embed run
/embed editembed channel messageid.
Here channel is the channel in which the embed you wish to modify is there. While message id is the id of the message with the embed. Example:
/embed editembed #verify 1061072341406330980
An example captcha. The answer is WFZVOP