Well gee willikers, I had the same question.
From the TechTerms website: "Sync" is short for synchronize. When you sync a device, such as a cell phone, PDA, or iPod, you synchronize it with data on your computer. This is typically done by connecting the device to your computer via a USB or wireless Bluetooth connection. For example, you might sync the address book stored on your computer with your cell phone to update the contacts. If you have an iPod, you may connect it to your computer to sync songs, videos, and other data using Apple iTunes.
When you sync a device with your computer, it typically updates both device and the computer with the most recent information. This is also referred to as "merging" the data. For example, if you have added a phone number to your phone since the last time you synced it with your computer, that number will be added to your computer's address book. Similarly, any numbers entered into the computer's address book since the last sync will be added to the phone. Most syncing programs also remove entries that have been deleted on either the device or the computer since the last sync.
As a newbie to smartphones (and yes, this is my first post too), the "typically done" makes me nervous. It's not a given. So is Samsung Galaxy S3 "typical?" I accidentally deleted many entries on my google calendar, but my Samsung still (thankfully) has the entries. Since the word "typical" was used in defining "sync", I want to make sure when I "sync" that google transfers to my Samsung. In other words, I want to make sure my Samsung updates Google with my Samsung entries. Essentially I want to make sure they will merge; entries on samsung will transport to google.
So please don't be harsh. I think this is a reasonable question to have been posed. I googled how to sync on Android and this website is the one that would seem to be the most helpful. Thanks...and "please be patient, God isn't finished with me yet."