Technology allows a caller to "spoof" or change the caller ID you see on an incoming call. Large companies have used this for years, legitimately, and now individuals can do the same thing, often for fraud or dangerous "pranks".
The incoming number can be changed to anything, and so can the caller ID readout. When you answer the call, you may see "police" or "mother". If they can't yet, someday soon they will match names from the reverse directory, so that Mr. Smith sees "Mrs. Smith" on the incoming caller ID.
The point is to get you to answer the call and/or convince you that the caller is legitimate. Crooks want you to divulge information that will help them steal from you.
Unfortunately, the telephone isn't what it used to be, and no one should answer a call unless they know who's calling. Even if the caller ID says "Fire Dept", firemen don't call to tell you your house is on fire. If the call is legitimate, they'll leave a message.