You have registered more than one top-level domains (same domain with different tld) but you don't want each of them domain to be simply parked or to just redirect in the main domain.

Example:

radio-expert.com (Joomla is installed here, is multi-language site English (default) and Greek)
radio-expert.gr

We would like to use the .com site for .COM and Greek language with .GR ! SEO result will be better for Greek language viewing the site from a GR domain. This is not rule but I suggest it.

So, a Joomla Multi-language default behaivour is to click on the language switcher module and changes the lanagues
http://radio-expert.com/en or http://radio-expert.com/el

So with the Multi-language Parked Domain Switcher plugin you can convert the links to

http://radio-expert.com/en/my-page-en

http://radio-expert.gr/el/my-page-el

IMPORTANT NOTE: All other domains must be "PARKED" in master hosting account, if you have cPanel is very easy to do it.