ccTLD stands for country code top-level domain, and is a category of domain extensions maintained by the Internet Assigned Numbers Authority (IANA) to classify the Internet.
Unlike gTLDs (generic top-level domains) like .COM, .BEER, or .PHOTOS, ccTLDs are all two letters long, and are all related to countries or independent geographic regions, e.g. .CA for Canada, .NZ for New Zealand, or .DE for Germany (Deutschland).
gTLDs have consistent policies governing them, because they are all under ICANN's purview (that's the internet's governing body). Also, gTLD registries usually manage many gTLDs.
However, nearly all ccTLDs are governed by their own country-based registries, which set their own prices, processes, and policies. This is why the registration information and fees, transfer process, and other functions for a ccTLD domain can be very different from your other domains.
Because many ccTLDs are made up of common endings to words, particularly in English, a few ccTLDs have become popular for domain hacks.
Here are some examples of ccTLDs that can creatively be used for domain hacks:
- .es (Spain): mak.es, bak.es, flak.es, cak.es, tak.es, cod.es, dat.es, pag.es, pi.es, stor.es, smor.es (yum), veggi.es, whistl.es, [YOURNAME]lik.es
- .is (Iceland): chris.is/moving, mike.is/blogging, soccer.is/awesome, domainhacking.is/exciting
- .io (British Indian Ocean Territory): rad.io, pat.io, tr.io, rat.io, aud.io, cheer.io, portfol.io, scenar.io, card.io
- .ch (Switzerland): ea.ch, ou.ch, mu.ch, hun.ch, bun.ch, lun.ch, bot.ch, por.ch, rea.ch, psy.ch, quen.ch, stit.ch, retou.ch, overmat.ch, workben.ch, laun.ch, ostri.ch
- .se (Sweden): adverti.se, wheelhou.se, hor.se, despi.se, disea.se, presi.se, verbo.se, brui.se, grea.se, impo.se, mous.se, prai.se, revi.se, cau.se, cha.se
If you're interested in reading more about the subject, here are some handy links: