about file types

[html20009876]

My friends,
I need to install a shopping cart for a small business now, I downloaded a package (OpenCart), which is similar to phpbb, and viewed files in the package.

I found many types of files in the pack.
I know php, HTML with java-script, but I don't have any experience with following files:

1. asp - can I use UNIX host for using asp file?
2. json - what does the file mean?
3. tpl - code in the file looks like php, are they same? any different?
4. xml - what does the file mean?

Thanks for your answer.

[ZABI]

ASP = Active Server Pages Requires IIS
JSON = JavaScript Object Notation
TPL = Document Template
XML = Extensible Markup Language