Pokémon Gold and Silver, and are a lot different (and better!) from Red/Blue/Yellow. Your trainer starts out with one of 3 brand new Pokémon:
1. Totodile - the water dragon
2. Cyndaquil - the fire mouse
3. Chikorita - the grass monster
Younew trainer start out with some Pokégear, including a cell phone type device that allows you to call home for advice, call friends, or Prof. Elm. Prof. Oak will give you your Pokédex as well.
Filled with new regions, Pokémon, players, people, badges, leagues, secrets, pokemon, and adventures, Gold and Silver is the new opportunity for all trainers, young and old. (well, not really....don't give this to your grandfather or something) It also has solutions to those annoying problems that were in red/blue/yellow. For example, you had to go into the menu to select cut, teleport, dig, surf, or any other HM. In Gold and Silver, you just go to the obstactle you want to use it on (rock, boulder, water, etc.) and press B or A and it will automatically work for you. Also, "registered moves" is where an item such as Bicycle or a rod can be set to select so when you press the select button, you can use that item right away. This makes things ALOT easier.
New mechanics are added to the games as well. For example, you set a clock and a calendar when you start that affects when certain Pokémon can be found. There's also a new "experience meter" that tells when your Pokémon will reach the next level by experience. Also, your Pokédex displays different info, pictures, etc. depending on which version you have. In Gold, pokemon will have a different battle position when you come across them than in Silver.