Not a dumb question. Easy answer!
Pleasure Island (PI) is the bar district AT Downtown Disney (DTD). Downtown Disney is made of up of the West Side (DisneyQuest, Circa De Sole, lot's of shops and restaurnts), the Marketplace (on the east side, more Disney-oriented shopping like Pooh Corner and the
lego store, plus restaurants like Fultens and Rainforest Cafe), with PI stuck right in the middle. It's all together a fun place, with lot's of free stuff, and some nice (slightly pricey) diversions from the parks.
The Boardwalk is a shop and restaurant district in the rear of Epcot, part of the Resort complex that includes the BC, YC, and BWV. It's made to look like turn of the century Jersey Shore. They have bars, restaurants, street performers, a dance club, and the infamous Surreys. Make sure one doesn't plow into you while you're walking around. It's a great diversion while you're at Epcot and need to get out for a while. It's also a great alternative nighttime activity.
Costs: For PI, it's around $20 to get in (opens at 7 at night), plus whatever you eat and drink. DisneyQuest (an interactive theme park) is around $30 for a day. I have no idea how much Circa De Sole is (never had any interest), but it's the most expensive of the bunch. Everything else is pretty much a matter of how much food or stuff do you want to buy. Things like the Lego Store are both a shop and a free play area for kids. The Dance Club at the Boardwalk has a cover charge, but it isn't much. DTD comes alive late morning and runs until late at night. Boardwalk, except for some breakfast stuff and lunch, doesn't really come alive until mid-to-late afternoon, but it's still fun to walk in the morning hours.
Pat