There are situation when we get confused about a DLL or a service or a file with unknown extension. regarding unknown extension you may check How to Open a file with unknown Extension. This Uniblue website will provide detailed information about them.
dll Library: This website provides detailed information about DLLs and the security risks, This site is continuously updated with new information.
Process Library: If you check your computer for running services you will be finding some names which are not common, it can be a useful service or can be a virus too. Some services can be stopped to increase the performance of the website. For that first you want to know more about those services. Check this section for knowing more about them
File Extension Library: This library will provide detailed information about file extensions. Once again we prefer you to check the link given above on the first line for this, which not only tell you what file is that but also help you to find the application required to open the file with specific extension.