Chinese languages are typically written in Chinese characters, which are logograms where each one represents a syllable. The vast majority of logograms represent a single morpheme, too, but there are some exceptions (bisyllabic morphemes and bimorphemic syllables written with two characters, and some characters that represent a polysyllabic word or phrase). About 20% (and 30% of the 500 most common) of characters have multiple readings – often these readings are similar in pronunciation and meaning, though.
Some characters were originally devised as pictographs, i.e. they were a drawing of the thing represented. Some others were ideograms, or basically an icon representing the concept. The vast majority of characters were devised by borrowing an existing character for a word that sounded similar, and adding an extra component to represent the new character’s meaning. As such, most Chinese characters have both phonetic and semantic components. In most cases, the semantic component is also the radical that characters are listed under in dictionaries. Due to sound changes over time, the phonetic component is generally not exactly the pronunciation, but just a clue.
There are currently two major varieties of Chinese characters: simplified characters, used mainly in mainland China, and traditional characters, used mainly in Taiwan, Hong Kong, Macau and parts of the diaspora (e.g. in southeast Asia, with very long-standing and well-developed Chinese communities – although since the 1980s both Singapore and Malaysia have shifted to teaching simplified characters in their school systems). The existence of the two types of characters is a hindrance to written communication; someone who is experienced with both systems can transliterate between them without much difficulty (albeit a lot of hassle), but machine translation between the two systems is not great because there isn’t a 1:1 correspondence between traditional and simplified characters.
There is, naturally, debate between advocates for simplified and traditional characters as to which system is better. Supporters of simplified characters make arguments like simplified characters being easier to write, easier to distinguish especially at small font sizes, reflecting variants of characters that in many cases had long existed anyway, and in some cases are more logical (e.g. the phonetic component of characters being updated for more modern pronunciations). Proponents of the traditional characters argue that in an era of IMEs the difficulty of writing characters is not a concern anyway, that some of the simplified characters are pretty difficult to distinguish from each other too, that the traditional characters embody centuries (or millennia) of layers of meaning in terms of the components that make them up, that the phonetic reforms are Mandarin-specific and run the risk of marginalising other Chinese languages, and that retaining the traditional characters doesn’t break the connection between modern and historical forms of Chinese, or with Chinese characters where still used to varying extents in Japanese, Korean or Vietnamese.
Over 2,000 Chinese characters remain in widespread use in Japanese, which refers to them as kanji. Many kanji are also simplified compared to traditional Chinese characters, but not always the same ones, or in the same way, as mainland China’s simplified characters. In South Korea Chinese characters (known as hanja) also also sometimes used, generally in names (of people, places, etc.). In Vietnamese, which knows this system of writing as Chữ Nôm, Chinese characters are no longer in general use (since French colonial times Vietnamese has been written in the Latin alphabet) but they are still used in some traditional or ceremonial contexts.