I use Pinyin (i.e. a romanization standard of Chinese characters) to type in an IME (input method environment). The IME suggests characters and words with that romanization from its database, which I can then select.

An average native Chinese speaker knows anywhere between 3000 and 8000 Chinese characters. For daily communication, 3000 is more than enough.

I cannot answer for Japanese because I don’t speak it. I do speak a bit of Chinese but I’m still learning. Chinese uses pinyin (拼音) to input characters on a computer. That means that you “build” your characters by adding lines on top of each other to form the final character. You need to type on multiple keys to build one character. Pretty much like some European languages adding accents on plain letters by pressing the accent key and then the letter. Chinese is easy to use since some words are only one character or 2. I can compare pinyin system to old phones with ABC on 1, DEF on 2 etc. After it’s muscle memory like the rest. It takes time but once you get it, you can type very fast. It’s a very simplified explanation. Look into pinyin online to dig deeper if you want to As for the amount of characters used, I think it isn’t very relevant to think that way. As opposed to latin languages and their letters, characters have a meaning alone and grouped. Each character can be used more or less frequently depending of what you are doing or what is the topic you are writing about.

Again, I’m not a native speaker but languages is my job and passion. My colleagues from China explain it that way, but it might be very simplified. Im sorry if something isn’t 100% accurate or wrongly worded. Hope this helps

Edit: typo

Japanese uses 3 writing systems - hiragana (think of it as the “default” system), katakana (used for loan words from other languages or onomatopoeia), and kanji (Chinese characters - used for nearly all type of words). Hiragana/katakana you can sort of think like an alphabet but each character is actually a vowel by itself or a consonant plus a vowel (eg ki, mo, ri). Building a word is just batching these guys together.

The IME takes input in hiragana (the type on the keycaps you see) and types out to hiragana by default, and detects what word you’re typing. You can then hit a key to make a drop down menu appear, so you can flip the hiragana into katakana instead or grab the correct kanji.

So for example, in default hiragana:

としょかんにいきましょう！ (Let’s go to the library!)

Will turn into:

図書館に行きましょう！

The IME detects the としょかん input as meaning “library” and will provide the proper kanji 図書館 in menu. However if you wanted it in katakana for whatever reason, it will also automatically offer トショカン as an option. Likewise for いきましょう (let’s go) the core word is いき -> 行き so it’ll swap in the kanji as an option.

So unlike Chinese typing you don’t build an individual character with a list of radicals plus handy autosuggests - it goes by word!

u/mignyau gave a pretty good thorough explanation above, but a couple points of clarification:

hieroglyphs - The Japanese script you're likely referring to are called "kanji" and are technically considered "logographs". Hieroglyphs are a very different type of symbol.

Totals - there have been WAY more than 1,000 kanji in existence throughout the Japanese language's many years of standardizations and revisions (there is no definitive number). However, a little over 3,000 kanji are readily used in common communication nowadays.

Typing - most people typing in Japanese today use an input method called "romaji nyuuryoku" (romaji input). "Romaji" is a method of writing Japanese that uses Latin script (a,b,c's) to write out Japanese. For example, "arigatou" is the romaji writing of ありがとう. A piece of software on most Japanese computers/devices then converts the romaji into kana (Japanese phonetic script) or in some cases straight into kanji where appropriate. That's the basics of it, at least.

As with most things that you grow up doing in your life, you get used to it with enough repetition.