Upload Dir: '$upload_dir' : Directiory where the uploaded file will placed.
Input Field Name: 'file' : File input field name.
Rename : True for rename file if some is exists. Or if you want to give new file name then just write new file name rather than "True"
Replace: If file exists replace or not.
Max File Size : 0 denotes default value.
Check for Types : "jpg|jpeg|gif" i.e. funcction will check of these file extensions.
if it is ("doc|txt|rtf") then it will check the uploaded file having any of these extensions.