How Can I Communicate Via A Webcam?

Yes, you can it.
Bye webcamera, it can be Logitec, or A4, or another producent.
After installing (using attached manual) Than, You must search and download Skype & install this program. Your sister must make all the same.
Go! I'll glad to see You in Skype network. My nick is olegkats1, Ukraine.

It sounds as those your question has been answered but I am concerned that folks are only letting you to the applications they use. Just to confirm, 1) Both you and your family (sister) need to have a webcam properly installed on your system (mac or pc, does not matter). Purchase the that has the features that best suite your needs (I also suggest getting one with a built in microphone so you can talk as well as look) and will work on your system.  2) Each system needs to be connected to the Internet. The higher the speed the better as sending images takes more bandwidth. Generally, the higher the speed, the bigger the bandwidth as well.  3) each system needs to have the same application that has the capability of sending webcam, voice and instant messages. There are a couple listed above but if you do a search on the web, you will find many more. Just make sure they are both mac and pc compatible versions. 4) Each of you will need to create a user ID in the application and share your ID with the other so you can find each other within the application (when the other is connected, of course).

I travel a lot for work and have a webcam on my laptop and put one on the kids home pc so that I can talk to them even though I am not there. It has simplified life greatly. We both are on windows based machines though so finding applications became a little easier. Aol's AIM program, Windows Messenger or Yahoo Messenger.

You need an Internet connection, high speed works the best for this.  You'll also need a software program, which may have come with your camera. If not, check out Sightspeed.com.  They have a free version which works fine.

Webcams typically take the form of small camera connected directly to a pc. They are connected to a video capture card and directly to an Internet.