A solid line means each bus travels the section of this route, and a dashed line means buses travel this section at certain times or on certain days.
The circled letters along the route indicate a stop where the bus is required to be at a certain time. The letters correspond to the letters at the top of the timetable columns. Using these together, you can determine how long it takes the bus to travel different route segments.
Suggested transfer points:
The boxes with a "T" followed by a route number or name indicate where the route on the map intersects with another Big Blue Bus service the most frequently. While you can transfer anywhere you want, these are typically the easiest places to catch one of the other services noted.