Friends to be Made
These characters are potential Friends of the Player. They have a Friendship Meter (viewable in the pause menu), and some even have gifts for the player upon reaching certain friendship milestones. Once per day, you can speak to them to raise this meter by one point; you can give them a Can of Maple Syrup for an additional point that same day. Friendship points can be lost by spitting on people, one point for each time spat.
Non-Friendable Characters
These folks aren't necessarily mean or unfriendly, they just don't have a Friendship Meter in the menu. You can speak to them, regardless, and they'll usually have something to say back.