Why buy expansion?
I have the free app and am playing a few single player games after my 'sun' recharges.
Why exactly do the 'expansions' provide in the Catan shop? I can't find any information on exactly what functionality they add, can you please advise.
'the game - 500 Gold'
'special scenarios 1 - 300 Gold'
When you buy the base game, and the various expansions, it allows you to play unlimited single and multiplayer games (up to 6 players) in the scenario you purchase.
First you buy gold on whichever platform you use (Android, Apple, Steam), then use the gold to buy the expansion(s) you want. If you are interested in more than just the base game, I would recommend getting buldles (both gold and games) to save yourself a few dollars.
Keep in mind that many of the City and Knights scenarios require Seafarers to play. People usually start with the base game, then Seafarers, then Cities and Knights. The special scenarios (Enchanted Land and Great Canal) require all three of the other expansions.
There are also the stand-alone expansions Inkas and Rivals. Inkas is like Catan, but set in the Andes and instead of building one set of settlements and cities, you build three sets. Each older group falls into ruin when you progress to the next stage. Rivals is based on the two player card game. I don't play that one, so can't tell you much more about it.