You are Hawke, the Champion. Either a female or male human, you have risen through the ranks of society and your influence has grown as a result. Told through a framed narrative (think the movie Princess Bride) by a Chantry member named Cassandra and a dwarf named Varric, the story of Dragon Age II is dictated backwards – you are already the champion in present day and Varric is re-telling your story.
What this means for players is that instead of spanning one year like Origins, the second covers 10 years of events. This also grants BioWare the freedom to skip over the "boring" sequences that don't offer compelling gameplay and means that your choices will have more of an immediate impact than in most titles.
From what I saw, Dragon Age II is linear, yet open. Points A and B are predetermined, but how you get there is entirely up to you. During my time with the game I recruited people in the order I wanted to and completed missions the way I wished as well.