Unconfirmed transaction, in memory pool

Hi guys,
I’ve got an unconfirmed transaction, IN MEMORY POOL.

Status: 4/unconfirmed
Date: 21/02/2018 18:43
To: LR6rFyZ5uWazDqQLt6SMgtmJaCVrynKiDp
Debit: -0.10000000 LTC
Transaction fee: -0.00452000 LTC
Net amount: -0.10452000 LTC
Transaction ID: 8c93a98da06bce95e7eaee3376f53f8a6cfc605611956aa78a62a7be5b560bd5
Transaction total size: 225 bytes
Output index: 1

12 hours passed, not much value in it (it was a test one) but I need to understand what happened.
I visited site “https://live.blockcypher.com” to check the amount of LTC on my wallet, the amount is like BEFORE my transaction, while on my LITECOIN CORE, the amount is like AFTER the transaction.
But I can’t abandon the transaction (the command is present but “grey”)
I thought my transaction was not part of blockchain yet, I cancelled the file wallet.dat and replaced it with a back-up performed before the transaction… Nothing! The transaction is still present.
I’d like some experienced guy to explained to me:
1- What this memory pool is, what changes between beeing in or out of it
2- What is the method to erase a transaction using Debug window -> Console, and I’d like to know if in my case (in memory pool) it is possible to erase it.
Again, it is very strange that the LTC amount on " https://live.blockcypher.com" is BEFORE transaction: since it is not confirmed, why I can’t cancel it?
Thanks for any kind explanations
Simone from Italy

Updating: transaction just confirmed! But please if someone skilled can answer my message anyway, I’d appreciate it a lot!

I am having the exact same problem right now. The transaction was done yesterday 16 hours ago and now the coins are sitting in the memory pool. Can you please let me know how long it took for you to confirm the transaction?

Cheers,
Jackie

24 hours. In my case I think the delay was caused by the little amount I was moving. Just relax and wait, your money will appear soon.

I have mine as well. A little than 24 hours. Thank you indeed for your kind assurance.