Revoke Title: Removes a title from a targeted vassal and take it for yourself. If the vassal refuses then you merely get a claim on his title instead.
Create Title: If you own a lot of land (like maybe half of Sweden) and no one has the title “King of Sweden” you can create that title for yourself.
Usurp Title: When you control more than half of the land of a province/country, you can claim being the lawful owner of a title, even if it is held by another Character. This is called “usurping” the title and gives you a legal claim on the title, but not the title itself. You will have to earn the title by conquering the province by warfare.
Grab Title: A megalomaniac (or even you) may say that a title is theirs without having a legal claim to do so. This costs quite a bit of Prestige, but allows the character to declare war.