The dictionary attack is a very simple attack mode. It is also known as a “Wordlist attack”.
All that is needed is to read line by line from a textfile (aka “dictionary” or “wordlist”) and try each line as a password candidate.
There are techniques floating around that exploit the ] function in oclHashcat to enable it to do a Dictionary Attack. Note that this was developed in the early days of the old oclHashcat-old when there was no oclHashcat. Nowadays there is no more need for it.
Our recommendation: Do not use it. Use oclHashcat if you want to do a Dictionary attack on GPU.