Early adopters, users willing to join and explore a new social platform at public launch, are like adventurous travelers. They enjoy going off the beaten path and discovering new things. Adventurous users are important because they will tell their friends at home about the cool new things they discovered when they were exploring. This encourages their friends to try the new thing, too.
Beta users are a bit different. They’re like the friends and family you invite to your new bed and breakfast in a jungle in Costa Rica right before you open to the public. They understand you’re working out the final kinks and are willing to help do that. If the complimentary breakfast is a little underseasoned or if the water pressure in the shower is too low, they will let you know so you can fix it.
Alpha testers are a whole ‘nuther breed. They show up while you are still building your new bed and breakfast, putting in the roof and windows, etc. Some bring their own toolkits to help build. They get to work right away, kicking at subfloors and tugging on wall cabinets to see if anything falls over. They’ll test and give feedback while you literally build the structure of your bed and breakfast right around them.