Skype is available as a free download from skype.com. Click here to go straight to the download page. To download and use Skype you will need to create a free account. During the account creation process you will be asked to invent a Skype username. This username is your unique Skype identity, and can be thought of as being the same as a phone number. Please note that there is no difference in performance between the free and the premium versions of Skype.
Yes, Skype meets all the currently applicable security and quality standards set down by the relevant regulatory agencies. Communications over Skype are protected by 256 bit AES encryption. This means they are secure and can not be listened in to. VGA picture quality (640x480) is generally achievable with high speed Internet connections giving even better image results.
Skype is a point to point technology. A connection using Skype goes directly from the caller's computer, to the recipient's computer. There are no intermediary steps. This inherent design feature makes any communications over Skype extremely difficult to eavesdrop on. The extraordinary volume of calls conducted over Skype every day makes the task of finding a specific conversation akin to finding the proverbial needle in a haystack.
Even if a hacker was able to surmount these obstacles and tap into a communication all they would then see is a stream of encrypted traffic. Using the fastest computers now in existence, it has been estimated a brute force attack on a single AES message would still take longer than the entire lifespan of the universe to perform.