Social engineering is a term that refers to manipulating or tricking someone into sharing information. It’s very popular, because it’s usually much easier to fool someone into handing over their password than it is to hack their password (unless the password is really weak). Social engineering is generally highly convincing, sometimes made more believable by snippets of information which the fraudsters already have about you.
Once a hacker has access to your accounts (made easier if all your accounts are protected with the same or similar passwords) they can steal your identity. In other words they can impersonate you, sending emails to people in your contacts, or leaving messages ‘from you’ on their social media pages. Thus not only are you exposed to malware, fraud etc, but your contacts too.
Social engineering is generally highly convincing, sometimes made more believable by snippets of information which the fraudsters already have about you.