"The language of the Czech Republic is Czech."
Translation:La lingvo de Ĉeĥio estas la ĉeĥa.
I guess the Czechs, being Slavs, prefer the -io form, and not Ĉeĥujo (Slavic language speakers will understand me). ;)
"Ĥ" is a voiceless velar fricative...the sound doesn't come from the vocal cords (voiceless), but from air moving though a narrow channel (fricative) formed by the back of the tongue against the soft palate (velar).
Yeah, that's not all that helpful; try listening to some sound clips.
It is rather uncommon, as you might guess from the fact that they are using a country for it. And it's becoming more uncommon, with people changing words to use "k" instead, such as arkitekto for arĥitekto.