The following is a (non-exhaustive) list of computer science symbols/terms you may see during your career.
. (Unix Directory)
In Unix filesystems, the . symbol represents the current working directory.
.. (Unix Directory)
In Unix filesystems, the .. symbol represents the parent directory to the current working directory
. (Unix file)
In Unix filesystems, files beginning with a . symbol are considered hidden, and do not show up in standard file listings.