What does koto mean?
Koto is used in so may phrases...does it just mean 'things'? If I could think of some good sentence examples I would, but I don't know exactly what it is, so I find it difficult to use it myself.

I know it can nominalize a verb like 'no' can (食べること and 食べるの are the same, right?), but it's used in other situations too.

ありがとう。
Alright, thanks for the answers. I knew about ~koto ga aru, but I didn't know about the related to construction. That must be what I've been hearing.

I haven't used these forums before, so I don't know if you can ask another question in the same thing, but I was wondering when do you use no at the end of a question? What's the difference between no and ka? Formality? Can no only be used with dictionary forms and ka only with ~masu forms?

Question

What does koto mean?
Koto is used in so may phrases...does it just mean 'things'? If I could think of some good sentence examples I would, but I don't know exactly what it is, so I find it difficult to use it myself.  

I know it can nominalize a verb like 'no' can (食べること and 食べるの are the same, right?), but it's used in other situations too.

ありがとう。
Alright, thanks for the answers.  I knew about ~koto ga aru, but I didn't know about the related to construction.  That must be what I've been hearing.  

I haven't used these forums before, so I don't know if you can ask another question in the same thing, but I was wondering when do you use no at the end of a question?  What's the difference between no and ka? Formality?  Can no only be used with dictionary forms and ka only with ~masu forms?

Answer

In casual speech you don't really need to use "ka" at all. You just ask questions replacing desu ka/ka with a rising tone. たべる↑ = 食べますか。
"No" (or "na no" with na-adj and nouns) in the end of sentences with a rising tone shows curiousity or that you're seeking an explanation. It's the informal version of "no desu ka". It's often used with question words like nande and itsu. "No" can also be used in statements when explaining or emphasizing something. It sounds pretty feminine to just say "no", so guys say "nda" instead. It's really "noda", but when spoken it's easier to just say "nda". (Like the i in teiru -> teru)
You can't use "da" in a question though, that's why both men and women say "no?".

And yes, you shouldn't mix casual speech with polite speech.

Answer

I should add that ”食べること”　and ”食べるの” are not the same.

For example when asking "do you eat" you can say ”食べるの？”　not　”食べること？”
Or when speaking about something related to something or to someone you say ”あなたのこと” ("About you")　or ”食べること” (related to eating).

Answer

It can also be used in the sense of having an experience of having done something.
サラダを食べたことがある。 I've eaten a salad before. (I have had the experience of eating a salad)
行ったことがある。 I've been there before. (I have had the experience of going there.)
やった/したことがない。I've never done it before. (I haven't had the experience of doing that.)