As far as I can tell, an encounter in 4E is any set-piece obstacle or conflict designed by the GM and then sprung on the players. You can have roll dice for obstacles outside of encounters, for example, if a PC decides to climb a nearby rock face for a better view of the area, but I’ll probably tend towards taking a “Say Yes” approach to non-encounter obstacles unless they seem particularly interesting.
The different types of encounters that I can imagine are:
- no-roll encounters, resolved through free play;
- single-roll encounters, resolved with, uh, a single roll;
- multiple-roll encounters, resolved will multiple independent rolls;
- skill challenges, resolved with multiple connected rolls; and
- combat encounters, resolved with a map, miniatures, and a bunch of connected rolls.
However, there are a few problems with the way most encounters are written in adventures. First off, it seems like there are a lot of things that are basically encounters that are not really treated as encounters or written up as such. For example, there might be a description of how the PCs meet somebody and that person tells them some information and maybe even gives them more information if they make a certain skill check. As far as I’m concerned, that’s an encounter. It’s something the GM plans ahead of time and it’s something that could have multiple possible outcomes that affect the way the narrative builds.
Secondly, if the GM and players are really supposed to implement encounters dynamically in play, it would be really helpful if each encounter was written up in multiple possible forms. Not every encounter would necessarily need to have five different versions to choose from, one for each of the different types of encounters, but having at least a few choices would make pacing games or tuning them to the tastes of individual GMs and player groups much easier. Maybe you don’t want to fight the zombies, but decide to sneak past them instead. You could even have an encounter that began as a single roll, but would escalate to a skill challenge or combat if the roll was failed (or passed!).
Thirdly, the clear difference between powers and skills makes shifting between these different types of encounters somewhat difficult. For single-roll, multiple-roll, and skill challenge encounters, PCs roll skills. For combat encounters, they use powers and sometimes also roll skills. Most powers seem to be useless outside of the battle map, which is really strange if they are things the PCs should just be able to do at any time. I propose that most powers should have a non-combat use or be tied to a specific skill, so they also prove useful in non-combat encounters. If I have an encounter-based power, why shouldn’t I be able to use it in a skill challenge?
Finally, all maps should be provided at full, reproducible size, so they can be printed out and used in play. And all monsters / hazards / obstacles should have their stat blocks provided with the encounter.