Something like "The baby was born." or "The house was built." There's no person in the sentence actually doing the action. What do you call this type of sentence?
 The baby was born.
 The house was built.
These are both called short passives, the type of passive where a by phrase can usually be optionally omitted, cf. The house was built in 1960 (by a reputable local builder).
In your first example with "born", no by phrase would be possible, cf. *"The baby was born by a Greek peasant".
The sentence is written in passive voice.