What is Skype, how does it work and does it cost money?

I'm kind of confused about Skype. My friend said that it's free and some told me it cost money? How does Skype work? If I want to webcam chat with my cousin in Hong Kong, is it free or do I have to pay a fee or something. Can someone please simplify...

does it cost money a month to use? or just if you use certian featurs. it says skype to skype is free and skype to mobile, there is a fee. but does it cost money just to have??

I know it's free to make Skype to Skype calls, but if I used my iPhone to call someone's computer does it cost money? Also since I'm using my phone and I know that calling someone's phone number with Skype costs money, is that the same case here?

I am thinking of canceling my landline and setting up a Skype number and account to call other landlines in my area. Does it cost money for the other landline phones to receive my Skype call?

using regular phone service does it cost me additional money to call a skype number?

I just got a skype and I called someone. Since this is the first time I do it, does it cost money?

I downloaded the skype mobile app on my phone to video chat with a friend but it didn't tell me if it would cost me any extra money? I don't plan on calling people on it. Just video chat. Same with the oovoo app I downloaded. I just want to video chat...

I downloaded the skype mobile app on my phone to video chat with a friend but it didn't tell me if it would cost me any extra money? I don't plan on calling people on it. Just video chat. Same with the oovoo app I downloaded. I just want to video chat...

I thought Skype 5.0 came with multiple people video chat. Does it cost money to video chat with more than one person at the same time?