By default, the touch command changes the modification and access times of the file.
If the file does not exist, it will be created with default permissions.

• Create the file if it doesn't exist.
  $ touch file1 $ ls -l file1 7 Jan 07:32 file1
  
• Do not create the file if it doesn't exist.
  $ touch -c file2 #file2 doesn't exist im my system, so because of the option "-c" it won't be created. $ ls file2 ls: file2: No such file or directory

The following options can be used:
-c |Do not create the file if it does not exist. -a |Change the access time of the file. |The modification time of the file is not changed unless the -m flag is also specified. -m |Change the modification time of the file. |The access time of the file is not changed unless the -a flag is also specified. -h |If the file is a symbolic link, change the times of the link itself rather than the file that the link points to. |Note that -h implies -c and thus will not create any new files.