This naming convention comes from Unix-like operating systems (such as Linux or OS X), where it means a "hidden" file or directory. It works anywhere, but its primary use is to hide configuration files in your home directory (e.g.
~/.plan – they're frequently called "dotfiles").
Dotfiles could, in a way, be called the traditional Unix equivalent to the "AppData" directory on Windows. (Many Linux programs are being changed to follow the XDG base directory specification, moving their configuration to
~/.config/ and other data to
~/.local/share/ – this makes it a little more similar to
You have these
.subversion directories on Windows because you've used some programs – specifically, OpenSSH and Subversion – that have been ported to use Windows system APIs rather than POSIX ones, but haven't been adjusted for some other Windows conventions.
Sometimes this adaptation is skipped intentionally, to make life easier for people who use Unix-like environments such as Cygwin on their Windows systems. For example, Cygwin installs the standard set of Unix-like tools like
ls, which ignores the Windows "hidden" flag and only honors the
.dotfile names. Also, using the same location (e.g.
<home>/.ssh) can make it easier to synchronize configuration between one's Windows and Linux/BSD/OSX computers.
Also: Typically these files are in the user's home directory, e.g.
/home/name/.ssh on Linux, or
C:\Users\name\.ssh on Windows 7+. It is quite rare for them to be put in the "Documents" or "My Documents" subdirectories.
As Rob Pike writes on Google+, this was an accidental feature:
Long ago, as the design of the Unix file system was being worked out, the entries
.. appeared, to make navigation easier. I'm not sure but I believe
.. went in during the Version 2 rewrite, when the file system became hierarchical (it had a very different structure early on). When one typed ls, however, these files appeared, so either Ken or Dennis added a simple test to the program. It was in assembler then, but the code in question was equivalent to something like this:
if (name == '.') continue;
This statement was a little shorter than what it should have been, which is
if (strcmp(name, ".") == 0 || strcmp(name, "..") == 0) continue;
but hey, it was easy.
Two things resulted.
First, a bad precedent was set. A lot of other lazy programmers introduced bugs by making the same simplification. Actual files beginning with periods are often skipped when they should be counted.
Second, and much worse, the idea of a "hidden" or "dot" file was created. As a consequence, more lazy programmers started dropping files into everyone's home directory. I don't have all that much stuff installed on the machine I'm using to type this, but my home directory has about a hundred dot files and I don't even know what most of them are or whether they're still needed. Every file name evaluation that goes through my home directory is slowed down by this accumulated sludge.