What exactly is meant by a personalised spear phishing email?

The email refers directly to the recipient, through the salutation, reference to colleagues / acquaintances / superiors, reference to interests / hobbies / skills. 

In contrast to mass phishing (first the email is created, then sent out en masse), with spear phishing the attackers first look at the recipient and try to create an individually tailored email with a high success rate. 

We have written a blog entry about this https://it-seal.de/en/spear-phishing-malware-from-your-boss/