Last week I created a 0.191 btc transaction with 0 tx fee -- moving btc from one wallet to another -- and the transaction never posted to the blockchain -- 0 confirms.

Today I downloaded and installed version .9, and I was looking through the menu options and a saw "Clear All Unconfirmed", so I clicked on it and got the message that unconfirmed messages would be cleared and I can retry "stuck" transactions.

My understanding is that the transaction would have been posted to the bitcoin network and gone into some miners queue to eventually be added to the blockchain, and that because of the 0 tx fee, it may take some time (as long as five days, from what I could ascertain from the forums).

Here are my questions, stemming from my imperfect knowledge of the bitcoin protocol and operation of wallets:

What is a "stuck" transaction and how does a transaction get "stuck"?

Where is a transaction "stuck"? In the wallet? Does a "stuck" transaction get transmitted to the bitcoin network?

Is it possible that my 0.191 transaction is still sitting in miners queue, and may yet get added to the blockchain (it is more than seven days now)?

When I cleared unconfirmed transactions (the 0.191 transaction was cleared), does that mean than the unconfirmed transaction is cleared also from the bitcoin network (cleared from miners queue)?