I'm currently playing as King Malcolm of Scotland, at the earliest possible date. I appear to have a county to myself, and am surrounded by other Scottish counties. Because those counties are Scottish, and because I'm King, they're mine, right? And all the characters related to them are my subjects? I'm finding it very difficult to exercise any control, and I just think that because I've never played a game quite like this (in E.U. you have total control) I'm just not grasping a fundamental concept.
A good example of this is that a Scottish Prince appears to have a claim on Caithness, currently owned by Norway, but I've no idea how on Earth to use this claim to attack them. After reading around I saw someone suggesting sending my emissary there. But all he seems able to do is forge a claim, but I shouldn't need to forge a claim, because I already have one don't I? Well, not me specifically, because I'm King Malcolm, but the Prince, my brother has a claim. So, is that relevant to me at all? It must be because I get a notice about it. So how can I use this claim? Or because a different character has it, is it up to him? Even though he's my brother and also of Scotland?
I'm pretty confused.
Also, could someone help define the terms for me? What's a duchy, for example? So many terms are used and I just have no idea what they mean in the game, and looking them up doesn't help.
Demense and vassals
In EU3, if you own a province, you own it, and that's all there is to it. CK is absolutely about personal relationships. You have what you own, and you have the loyalties of others. What you own is called your demense. The people who owe you loyalty are vassals.
Your demense is a dependable source of tax money, and a dependable source of troops (which you have to pay for). It is good for it to be big, but not too big, because if it's too big, your vassals will like you less.
Your vassals are a less dependable source of tax money, since if you tax them, they will like you less. What they are a good source of is troops that you can raise, and trouble.
When a vassal is happy, he will let you raise a good portion of his troops as a levy. You don't have to pay for this even. It's his job to pay for the troops, it's what being a vassal is. You can use these to go conquer someone else. If this takes too long, your vassal will get progressively more displeased, but it takes a long time, and their memories of being displeased aren't long. Also, if it is you who is being attacked, your vassals won't get angry if you raise their levies.
When a vassal is not happy, he won't let you raise many troops, and he might rebel.
So essentially, your demense is your economic engine unless you want to try to get away with taxing your vassals, and your vassals are your military engine. Your demense is a backup military engine that you can use to augment your vassals, or when your vassals feel that they have done enough for you.
Having a lot of happy vassals is good, because you end up with an enormous military, which is good for both attack and defense, but it won't improve your economy much.
Courts and claims
Every holding (kingdom, duchy, county, barony) has a court. Your court is people sitting in your holding. It's also the rulers of your vassal holdings. So if you have a guy with high stewardship, you can make him your steward if he's running one of your holdings, or if he's in your court. If you want to make someone the ruler of a holding, you can use anyone in your court, or you can use anyone in your vassals' courts (your realm). So your vassals' courts are a source of people as well.
A claim is a valid cause for war. Some claims you get yourself, and some may be held by the people in your court. If a claim is yours, you get the benefit. If a claim is someone else's, and you go to war for it, you may not get the benefit, depending upon how you define "benefit". If you press a claim for someone in your dynasty, or for an area that you have a dejure claim on (essentially a core, to use an EU3 term), the claimant will be your vassal if the claim is for a title that's lower than yours. Meaning, if you are a duke, and your brother Bob has a claim on an adjacent county, and you press it, he'll be your vassal. If you have a dejure claim on a county and you press it for some random guy, he'll be your vassal. If you press a claim for some random guy, he'll end up independent.
So what does this mean? You can give yourself claims by fabricating them. You can give yourself claims by taking enough counties in a dukedom that you can create the duke title (or usurp (steal) it), at which point you have a dejure claim. You can give yourself claims by marrying someone with a claim, but this gets very complicated.
As a king, if you marry someone with a claim that can be inherited, your children will get the claim, but if you are not careful, and depending upon which parent dies first, they may inherit outside of your realm. Different inheritance laws can complicate things and I won't go into that.
The bottom line is that this game is different and possibly better than EU3, because it has a higher degree of strategy and complexity. You don't get colonization, but you get personal relationships, and that is something almost completely absent from EU3.