These commands are used to tell ftp what type of file is to be transferred, in order that the transfer will take place correctly.
If the file you are transferring is a binary or 8 bit file (for example an executable file or an archive), you should issue a binary command to ftp before the get or put, ie:
ftp> binary ftp> get paper.doc
To switch back to transferring ordinary text or 7 bit files, issue an ascii command to ftp.