where do unspent outputs come from? This post asks the same question: What is an &quot;unspent output&quot;? but the answers for me are completely incomprehensible, probably because I lack a key piece of knowledge.

I have read every article I can find on "unspent outputs" and with each I get more confused.  e.g. these:

https://www.r3.com/blog/2017/07/18/what-is-a-utxo/

https://bitcointalk.org/index.php?topic=2011399.0

Lets say I have 1 BTC in a coinbase wallet or similar.

Do I have any unspent outputs yet? 

If yes, who created it?

If no, how does one create an unspent output (or in what circumstance/use case are they created?

Can a single address have more than one unspent output?  If so in which circumstance?

Is there some article which explains these fundamentals in layman terms?

This one is on the general subject but doesnt mention unclaimed outputs:

https://en.bitcoin.it/wiki/Transaction

It says this:


  An output contains instructions for sending bitcoins. Value is the
  number of Satoshi (1 BTC = 100,000,000 Satoshi) that this output will
  be worth when claimed.


What is the relationship between claimed and unspent?

Is unspent unclaimed?  

How does one claim unclaimed outputs, and in what circumstance would they end up unclaimed?
You are just puzzling your self. We will start step by step.

What is Bitcoin output? 

An output is an amount that was sent (via a standard transaction) to a Bitcoin address.
So when I send some bitcoins the recipient address is output address and if the recipient didn't spend the input I sent, it will be unspent output.

What is the relationship between claimed and unspent?

it's just the status of the output.

Do I have any unspent outputs yet?

No, You have one input. and the sender has "unspent output" which belongs to you. 

If no, how does one create an unspent output (or in what circumstance/use case are they created?

When you make a transaction, you are creating outputs.
Unspent or claimed is whether the recipient spent the bitcoins or not.

Can a single address have more than one unspent output? If so in which circumstance?

outputs do not belong to addresses, but transactions. and a single transaction can have more than one output (e.g.) if you were sending for more than one address in same time.

Is there some article which explains these fundamentals in layman terms?

Mastering Bitcoin book.