Activists can be subscribed, unsubscribed, bouncing, previously bouncing, spam reporting/complaining or previously complaining. Here's what each of those mean:
Subscribed: They want to receive emails from you and are targetable in emails.
Unsubscribed: They do not want to receive emails from you, and you can't send them emails.
Bouncing: These are hard bounces, meaning their email address is invalid or no longer in use. This is the first time an email to this person bounced, and they are now on the global block list. More on the global block list here.
Previously bouncing: They are on the global block list because an email to them has bounced in the past, therefore they were unsubscribed. More on the global block list here.
Spam reporting/complaining: They marked this email as spam and were placed on the global block list for future emails. More on the global block list here. Note that this is not the same thing as an email being sent to the spam folder.
Previous complaints: They are on the global block list because they previously marked an email as spam, therefore they were unsubscribed. More on the global block list here.