Hi @leyla_rzazade
By specifying this, you indicates to SAS that your input file is a tab-delimited file, meaning each record in the table is one line of the text file and each value of a record is separated from the next by a tab character (-> tabulation key on your keyboard).
It can be seen as an alternative to the common CSV format, in which values are separated by commas or semi-colons, which can cause trouble as they are very common characters in text values.
Best,