This is the Yomega GR yoyo, of the Yo Mod series of yoyos. YoMods by Yomega is a series of three different yoyos that all have interchangeable parts so that you can switch them around between yoyos and then lose a bunch of parts and end up with a series of non-functioning yoyos. Especially if you are 12 and under! Ha ha. I'm just kidding. I know that unlike other people, YOU are actually a responsible person who won't lose all the pieces. I'm sure you have a special box or drawer. It's only all those OTHER irresponsible jerks that will lose all their parts and then complain. But seriously, let me tell you about the GR yoyo, and how the series of yoyos actually works. I'll stop hassling you now about losing stuff.
The Yomega YoMods were developed as a series of customizable yo-yos. This series consists of three core models: The GR (shown above), The BX2 and The Pro Speed. Each of these yoyos contains interchangeable spacers, pads and varying weight yoyo halves. By building this system with interchangeable parts, players can do things like swap the return system pads from the G-R (green) to the Pro Speed (black) to make it more responsive or put the spacers from the Pro Speed into the BX2 (blue) for a wider gap. By mixing and matching all three YoMods, players can create a customized yoyo with a customized performance to match their skill level.
The Yomega G-R is a light (60 grams) responsive yo-yo made with an 8 ball C sized bearing, grippy pads, narrow spacers and a weighted rim. The Green G-R is the fastest, lightest, and most responsive yo yo in the Yo-Mod collection. That means that this model is the yoyo to begin with if you are still learning and are an intermediate yoyo player. It will wake up when you tug on the string. It can still do all kinds of awesome yoyo tricks, and is designed to be easier to learn with. Use this yoyo to get your tricks down, and then advance to the other two yoyos. Or hopefully, buy all three so you can play with them all and customize them to your heart's desire.
If you are buying a yoyo, don't forget to buy a yo-yo trick book to carry with you, a yoyo trick DVD for at home, and extra yoyo strings. Learning new tricks makes yoyoing much more fun, and you'll need extra strings, because they wear out with regular use.