cat must be written lowercase. This command statement uses the concept of here documents.
The first part
cat << EOF means that
stdin (standard input) of the command comes afterwards. All that comes after the first line until the word
EOF is the standard input to the command
cat. Or from the documentation:
This type of redirection instructs the shell to read input from the
current source until a line containing only delimiter (in your case it's EOF) (with no
trailing blanks) is seen. All of the lines read up to that point
are then used as the standard input for a command.
The second part of the command
>> $log 2>&1 means that the output of
stderr both, should be appended to a file whose name is in the variable
Conclusion: A file like this is now generated:
the quick brown