There is good documentation for new users. For a quick hands-on tour of the product, complete with sample data, follow the steps in the Search Tutorial.
There is also a Splunk Enterprise Overview that contains a description of the product, its major features and components, and links to more detailed information.
You can read the free book here on how to use it:
As for functions, it has thousands. It is more like a platform. Ask yourself, "What can a database do?" It can do lots of things, it just depends on what you want it to do.
Splunk is the same way - but it does not use a database, it uses a store of flat indexed files.
Looking here might give you a great idea of a few of the things that Splunk can do:
Thank you for your reply, I am just trying to understand that splunk is application based or server based ?
I mean this application is used for server activities or application activities?
Everyone here has given great suggestions. I'd highly recommend you first run through the Search Tutorial and Splunk Enterprise Overview documentation that @ChrisG posted above. These will answer your most basic questions about the product and give you a much more comprehensive picture rather than asking each question individually on this forum. After looking through the documentation, then feel free to use this Splunk Answers space to ask specific questions that are not clear.
As addition to this:
Splunk Enterprise is a powerful and versatile search and analysis engine that lets you investigate, troubleshoot, monitor, alert, and report on everything that's happening in your entire IT infrastructure from one location in real time. It indexes data from any application, server, or network device that makes up your IT infrastructure.
Thank you, I am not understanding this sentence "It indexes data from any application, server, or network device that makes up your IT infrastructure". As unix server perspective what It can do? How we can utilize this application?