I've owned a copy for a few years (it was a gift from my brother) but never played it (at the time I was predominantly playing 2-player games with my wife). Last night, my wife, brother-in-law, and I gave it a go.
Settlers of Catan (SoC) is a building game. Players randomly gain resources (depending on where their settlements are located) and then use those resources to build more settlements or to expand a settlement into a city. Settlements and cities accrue victory points (VPs). You may also purchase Development Cards, which may provide additional VPs.
I'm not a big fan of building games - I prefer combat-oriented games - but this was enjoyable. In line with my preference, I kept trying to buy Development cards, some of which provide "knights." The person with the largest army of knights gets extra VPs. Elizabeth outdid me, however, ending up with the biggest army and the accompanying 2 VPs.
Although there is no direct combat, a player can steal from another player by using the thief. If you roll a 7 or play a knight card, you can move the thief piece next to another player's settlement. This prevents that player from receiving resources from that space. In addition, you can take a card from that player. I did this to Elizabeth early in the game, much to my regret. Throughout the game, she kept getting the opportunity to move the thief, so she targeted me. As a result, I tended to suffer from a lack of resources.
While I foundered, Elizabeth and Jimmy quickly built up their little realms and were tied at 7 VPs each (a player needs 10 VPs to win). Then Elizabeth pulled off a stunning turn. She built 2 segments of roads, giving her the longest road in Catan (worth 2 VPs, which she gained at Jimmy's expense). She then used the bricks to build a settlement, worth 1 VP. Total = 10. She was victorious so I declare her the Queen of Catan.