The Czech Republic is not a geographically large country, but it has a rich and eventful history. From time immemorial, Czechs, Germans, Jews and Slovaks, as well as Italian stonemasons and stucco workers, French tradesmen and deserters from Napoleon’s army, have all lived and worked here, all influencing one another. For centuries they jointly cultivated their land, creating works that still command respect and admiration today. It is thanks to their inventiveness and skill that this small country is graced with hundreds of ancient castles, monasteries and stately mansions, and even entire towns that give the impression of being comprehensive artifacts. The Czech Republic contains a vast amount of architectural treasure, as well as beautiful forests and mountains to match.
The country's official language is Czech, a Slavic tongue spoken by over 10 million. The Slovak language can also frequently be heard, especially in larger Czech cities, as there is a sizable Slovak minority within the republic, and both languages are mostly mutually intelligible to each other. Czechs are proud of their language, and thus, even in Prague, you will not find many signs written in English outside of the main tourist areas. Many older people, especially outside the larger cities, are unable to converse in English, so it's good to learn some Czech words or phrases before your arrival. However, most young people speak at least some English, as it has been taught in schools since 1990.
Many Czechs speak a second and often a third language. English is the most widely known, especially among younger people. German is arguably the second most widely spoken language among older people. Russian was taught extensively under communist rule, meaning most people born before 1975 speak, read, or understand at least some Russian (and often pretty well). However, the connection with the communist era and the Soviet-led invasion of 1968 (as well as with contemporary Russian mafia gangs) have given the language some negative connotations. Russian is also not very useful with younger people, as it is not, despite the common misconception, mutually intelligible with Czech beyond some similar words and phrases. Other languages, like French and Spanish, are also taught in some schools, yet you should not count on them being widely understood. Czechs also understand basic words or simple sentences in other related Slavic languages, including Polish, Ukrainian, Serbo-Croatian, and Slovenian.
Czech can be extremely difficult for English-speakers to grasp, as it's not an easy language to learn, and takes extreme patience and practice to master, especially if one is unfamiliar with other Slavic languages. However, if you can learn the alphabet and its corresponding letters with accents, then pronunciation is easy, as Czech is a highly phonetic language, with the stress falling on the first syllable. The concentration of consonants in many words could seem mind-bogglingly hard to pronounce at first, but it is worth the effort! Czechs highly appreciate foreigners who try to learn their language, even if it is only a few phrases or simple words.
Czech has many local dialects and accents, especially in Moravia and parts of Czech Silesia. Some dialects are so different that they can be sometimes misunderstood even by native Czechs from a different region. However, all Czechs understand Common Czech (as spoken on TV, radio, newspapers, and taught in schools) and should be able to speak it (but some remain too proud to stop using their local accent). Some are even unable to speak Common Czech, but still can write it correctly.
Compared to Czech, Slovak uses softer pronunciation with different accents and letters. While Czech and Slovak grammar and vocabulary retain many similarities, there are occasional words that have different meanings. To the bemoaning of older generations, many young Czechs and Slovaks born after the 1993 dissolution of Czechoslovakia have difficulties understanding each other.
In cities like Prague and Karlovy Vary, Russian is also sometimes overheard, due to the fairly significant Russian diaspora living in both cities. More recent arrivals by Ukrainian immigrants have also brought their language, and it can frequently be heard in the larger Bohemian and Moravian cities. Polish is sometimes heard in the Zaolzie border region in North Moravia, particularly around Karvina and Český Těšín, where bilingual street, building, and road signs are commonplace. One of the country's most prolific immigrant groups, the Vietnamese, own many small grocery stores and corner shops (potraviny) across the country, as well as many Chinese, Japanese, and Vietnamese restaurants. This group commonly speaks Vietnamese to each other in their stores or on the street, although many also speak heavily-accented Czech. Younger Vietnamese have completely integrated into Czech society, and are often bi or trilingual with Czech, Vietnamese, and English.