Now I'm trying to figure out what a wallet is and what I just did.
For most cryptocurrencies a wallet is a collection of private keys that give you access to the coins that have been sent to specific addresses. The wallet usually also provides a list of those specific addresses for which it has the private keys so that you know where to send coins (or where to have others send coins) such that you can access them. In many cases this is handled by software (although there are also paper wallets and brainwallets). When the wallet is software, it generally includes additional useful features such as but not limited to an intuitive method for creating, signing, and broadcasting transactions, as well as an address book of addresses that you been given to send coins to and a history of transactions sent and received.
Is there any kind of step-by-step, easy to understand tutorial that can break things down to explain what these wallets are and how they work?
The user interface tends to be intuitive for most people. Some wallets have better documentation than others.
Are they all different (like bitcoin-qt vs blackcoin-qt etc)?
Well, they are significantly different in that they each manage a different cryptocurrency. In addition, the developers of each altcoin have different levels of commitment to thier pet projects. As such, some do a better job of keeping their software up to date with the latest features and bug fixes than others.
There are also multiple types of wallets for some cryptocurrencies. As an example, bitcoin has Electrum, MultiBit, and Armory in addition to Bitcoin-Qt. While each of those wallets allows you to control bitcoins, the wallets each have their own set of features, and quirks.
I see the wallet on my desktop. I tested with one coin to start, which worked, so transferred the rest. I see my coins in there. But what exactly is a "qt"?
http://en.wikipedia.org/wiki/Qt_%28software%29QT is a cross-platform application framework that is widely used for developing application software with a graphical user interface (GUI)
What are "blocks of transactions" that I'm downloading?
I suggest that you read the whitepaper that first described how a decentralized cryptocurrency could work through the use of proof-of-work for a distributed consensus. It is generally referred to as the "Satoshi Whitepaper", or the "Bitcoin Whitepaper". You can find it here:
https://bitcoin.org/bitcoin.pdfThe blocks of transactions form the blockchain which is the consensus agreement on the ordering of transactions that solves the double-spending problem.
It scares me because it doesn't seem that secure if it's connected to the internet...how do people hack into exchanges and not into one of these wallets?
People do hack into these wallets.
With a wallet such as this, you get to be responsible for keeping your own money safe. You don't have to trust someone else and hope that they know what they are doing. It is up to you to make sure that you have sufficient security in place.
On the other hand, an exchange is a very publicly known place with a huge number of coins. There is therefore a lot of incentive for hackers to spend a lot of time and a lot of money finding ways to hack in, and they know where to look. A piece of software running on your computer is much less likely to draw the attention of a hacker who can find more valuable targets elsewhere.
An exchange also has to have automated methods of transferring balances between users, and automated methods of withdrawing your balance. Hackers can take advantage of these automated methods.
It is good that you are scared. Hopefully that fear will act as an incentive to take the time to learn about the various methods available to you for securing your money.
And how do I back up this wallet? I clicked "encrypt wallet"
That doesn't sound right? "Encrypt Wallet" should have asked for a password and then should have encrypted the private keys with the password that you provided. It shouldn't have created a backup. Encrypting the wallet is a good idea. It means that if a hacker does manage to get a copy of the wallet data files, they won't be able to use the private keys to take/spend your bitcoins unless they also managed to get a copy of your password.
and it downloaded as something like 'blackcoin wallet backup.dat' but I can't open the file (says 'there is no application to open the document'). What is this, and how do I utilize this, should something happen to my computer?
That sounds like you clicked on "Backup Wallet". If so, then this file should contain all of your private keys (along with some other useful information about your transactions). If your existing wallet data should be lost or damaged, you can re-install the software and replace the "wallet.dat" file in the data directory with the "backup.dat" file (rename it to wallet.dat when you put it in the data directory). This will allow you to re-gain access to your coins. You should create a backup on a regular basis (if the sum of the number of receiving addresses created plus the number of transactions sent exceeds 25, it's probably a good idea to create a new backup), and store a few recent copies offline somewhere secure.
