I can't understand what are you asking yet.
Differences: gTLD = Generic Top Level Domain, ccTLD = country code Top Level Domain.
What kind of service you want to add? Domain registration service?
gTLDs are all those "generic" extension, not related (or restricted) to a specific country. Like .com , .net , .org, .info and all the new ones released recently, i.e. .xyz, .club, .company, etc. They're generic and worldwide.
ccTLDs are the regional / country extension, such as .us , .cn , .it , .de , .fr , .co.uk, .in, .tv , .ca etc. They're strictly related to a region (such as .eu or .asia) or a specific country. Let's take .de. It's the ccTLD for Germany, .fr is for France, .us is for United States etc.