You can use any file in your current directory by specifying only the part of the absolute pathname that comes after the path to your current directory, without a slash at the front. This is called a relative pathname . Usually it is just the file name itself. A relative pathname never has a slash at the beginning. You can tell the command to give you various kinds of file listings, by specifying options , which are single letters preceded by a space and a dash.
Dot files are files and directories whose names begin with a period.
Many programs store configuration information in dot files in your directory. The normal ls listing shows just the names of the files, packed several per line. The ls -a listing shows one line of information for each file. The rest of item 1 indicates the access mode of the file. Date of most recent modification.