I saw someone use this line and sometimes I see it interchanged with EOF which I understand to mean end of file. What is the purpose of this usage?
cat something <<EOT
something else
EOT
the actual term is "here documents" which is used to redirect input to an interactive program (cat in this case)
It doesn't have any relation with EOF. its just a kind of label. you can use any word in that place.
some popular usage are ftp, database processing etc.
ftp -inv $host << FTP ## start of label, below command will be treated as ftp command not the shell commans
user $user $passwd
bin
put $file
bye
FTP # end of ftp commands
ls ## shell commands again
Or "here text".