Umask command controls the default permissions given to a file when it is created.
It is uses octal notation to express a mast of bits to be removed from a file's mode attributes.
if you run command "umask" in your terminal it will return
"0002" which is the octal representation of your mask.
This means that if you create a file this will have for example test.txt and run ls -la command you will see
-rw-rw-r-- user user X XXX-XX-XX XX:XX test.txt
Now remove your file test.txt and set your umask by yourself.
ls -l test.txt If everything went well you should see this
-rw-rw-rw- user user X XXX-XX-XX XX:XX test.txt
Now your file is writable by others too.
On the same way working umask 0022.
Try it and you will see.