Czechia has a population of around 10.9 million, about a third of whom live in the three largest cities: Prague, Brno, and Ostrava. The country is ethnically fairly homogeneous — around 90% identify as Czech, with Slovak, Romani, German, Polish, and Ukrainian minorities making up most of the rest.
Czechs have a reputation for being reserved with strangers, which visitors sometimes read as coldness. It's not — it's just that Czechs take a while to warm up, and they don't smile at people they don't know. This changes quickly over a beer. Humor is dry, often self-deprecating, and heavily ironic. The communist period produced a particular Czech style of absurdist wit — Milan Kundera and Bohumil Hrabal are its literary representatives; the films of Miloš Forman capture it on screen.
Religion
Czechia is one of the least religious countries in Europe. Surveys consistently show that fewer than 30% of the population identify with any religion. Roman Catholicism has the largest following, with small Protestant and Orthodox communities. The historical reasons are complicated: the Hussite movement of the 15th century, forced re-Catholicization under Habsburg rule, and then four decades of communist atheism all left their mark.
Language
Czech belongs to the West Slavic branch, closely related to Slovak and more distantly to Polish. Slovak and Czech are mutually intelligible — Czechs and Slovaks follow each other's television and have little difficulty communicating, even though the two countries split in 1993.