The Finder is a persistent application in OS X that provides you with quick access to your Mac's file system. This not only allows you to organize documents, but also provides distinctive interface elements such as the familiar Desktop, where you may store aspects of your workflow and access local and external hard disks and mounted shared folders.
The Finder should launch immediately when you log in to your account; however, there may be times when it either does not, or gets stuck in a loop where it may seem to start but then quit, only to try over and over again.
If these problems happen, even though the Finder will not open, other programs should still do so if launched. This being the case, you can usually tackle the inability to launch the Finder by using the Terminal utility to remove the Finder's settings files, since in general, damage to settings files is usually the root cause of problems where programs will not start.
Since the Finder is nonfunctional, you will not be able to navigate to the Applications > Utilities folder and will need to launch the Terminal by other means. One approach is to use another Mac and log into your system via SSH, but another option is to use the Spotlight menu to search for "Terminal," and then open the program when it appears as a search result.
With the Terminal open, you can now run the following two commands (one per line) to clear out the Finder's preference files for your account:
Keep in mind that these commands will only remove the settings for the current account in which you are logged in, so if you are having problems with a standard non-admin user account but are connecting via SSH with an admin account, then the above commands will remove the settings files for that admin account and not the affected one. In this case, you will need to run the following commands, replacing "USERNAME" with the short name (i.e., the home folder name) of the account experiencing the problem:
With these files removed, if the Finder does not automatically open, try clicking its icon in the Dock or logging out and logging back into your account.