I've been playing Terra maps since G&K, so i'll tell you what I know.
Like TheKingOfBigOz said its a map script, not a scenario.
Basically all major civs start on one continent while there is "uninhabited" continents (number and size vary).
The new world will usually have a majority of the city-states on the map, while the old world will have few to no city-states.
A note; is that most ai's will not colonize very much if at all
The strategies you could use is:
The Explorer, where you build a nice little empire and once you get caravels you focus on the new world, becoming a superpower thanks to resources. This strategy became preferable after BNW since you can supply your colonies with food & production.
The Imperialist, this strategy is where you either conquer/settle alot of your original continent, and then colonize alot of the new world. Usually you will be a significant power and then gain power, or you will already be a powerhouse, and then become OP or just not have to colonize much.
The Capitalist, this strategy is basically; Step 1: Colonize and work resources. Step 2: Trade extra lux's and useless strategic resources. Step 3 ?????. Step 4: Profit.
Polynesia, since polynesias ability allows them to colonize instantly, they have their own set of strategys.
Isolationist: Just send your settlers and warrior off until you hit new land and bam, you have your own continent, aside from city-states. You will also have barbarian trouble and alot of people say this will make you a powerhouse, but its boring. Its up to you
"I don't need this continent", this strategy involves you settling your capital in the old world, and then exploring the new world and settling it, not as isolated as the first but still very focused on the new world, but not as risky.
Half-Explorer/Half-Imperialist, this strategy involves you settling normally and choosing the option of whether or not to colonize, much more of a "normal" game, but not utilizing polynesia's full potential.
There is much more to talk about but this is already probably too long. I hope I helped and gave you some useful strategies and information.