grammar - What is "koto" used for?

I know "koto" means thing, but I've seen it used like this in my Self-Study Japanese book:

Nihon no koto ga yoku wakarimasu ka.

and

Chiimu no koto o kangaete imashita.

Does this mean Japan's thing or Team's thing? I don't understand. Also I can't use Kanji, just Hiragana.

Answer

There is 「こと」 that actually means "thing(s)" and there is 「こと」 that does not mean "thing(s)".

「ふたつのことをかんがえています。」 means "I am thinking of two things."

The こと clearely means "thing". In the following sentence, however, こと does not really mean that.

「すみこさんのことがすきです。」 = "I like/love Sumiko."

One could possibly translate it as "I like the things about Sumiko." but that would not be natural English, would it? We just often prefer to speak more indirectly than to say something like 「すみこがすきだ。」 all the time.

In neither of your two sentences, does 「こと」 really mean "thing(s)".

1. 
   

   「にほんのことがよくわかりますか。」

   
   


2. 
   
   

   「チームのことをかんがえていました。」

   
   

Sentence #1, unfortunately, is a mysterious sentence to us Japanese-speakers. I could only guess what it would mean in the world of Japanese-as-a-foreign-language. They probably want it to mean "Do you know a lot about Japan?" while it could only mean "Does it tell you a lot about Japan? (referring to a book or something)" to Japanese-speakers.

Sentence #2 makes perfect sense and it means "I was thinking about the/our team."

In either case, I did not use the word "thing(s)" in my translations. I could have used it but that would have only made my translations look wordy. e.g. "I was thinking about things regarding our team."

You will keep encountering the structure "Noun + の + こと" for as long as you study Japanese, and it will just mean "regarding (Noun)" most of the time.