The Energon Pub

I suggest you visit:
http://tfwiki.net/wiki/Main_Page
and read some of their articles about G1,G2 and continuities generally.
I'm sure that most of your questions will be answered.

And,ofcourse,welcome to Seibertron!

G2 was a series of toys and a 12-issue comic series from Marvel that came out between G1 and Beast Wars. It included several repaints of old G1 figures (Prime, Jazz, Sideswipe, Starscream, Ramjet, Constructicons, Aerialbots, Dinobots (minus Swoop)) as well as some great new molds. The color schemes throw some people off because many are brightly/neon colored, but overall it was a great line with some excellent figures. The LaserRod Optimus Prime (long nose tanker truck with lightup headlights, sword, and gun, and a plethora of spring-loaded weaponry) was one of the best figures in the line, and has been repainted several times.

G2 was also a great way for some of us collectors to get figures we loved from years ago without paying through the nose so long as we arent picky about the color or G2 classification. I was able to pick up G2 geastalt pieces at places like Swap Meets and Thrift stores because everyone is so G1 focused. Rightly so for those after the big bucks but I was thrilled to pick up 3 of the components for Bruticus for less than 10 bucks and even getting the wepons for g2 characters online is a little cheaper.
I love the G2 Hero Megatron figure I have and he's the centerpiece of my Megatron Collection. Lots of fun stuff in that line.

And G2 "Laser" Prime would go onto to become what is STILL one of the most popular (and coolest) Nemesis Prime repaints of all-time