Herodotus is considered the father of history because he is the first person to write what we would consider a real history. In addition, he is the person who wrote the first recorded instance of the word "history."
Before Herodotus, stories about things that had happened tended to be mythical (like the Iliad) or tended to be just exaggerated stories meant to flatter kings by saying how wonderful they were. By contrast, Herodotus tried to write a history that was truer and more objective. He used his own observations and the testimony of others to write his histories.
Thus, he was the first that we know of to attempt an actual systematic analysis, based on facts, of past events.
Herodotus is known as the father of history because he was the first historian to collect and systematically document events and create an account. He compiled these accounts into his single major work known as The Histories. This document contains records of politics, cultural traditions, and the geographical landscape of areas including Northern Africa, Greece, and Western Asia.
He relied on his personal observations and inquiries from natives to develop the records. This had an impact on the validity of the accounts but the work set a precedent for subsequent historical works, since it was the first in Western literature. He was motivated to capture the history of ancient times and to ensure that events were not forgotten. His motivations are well-captured in the beginning of The Histories where he states, “This is the showing-forth of the inquiry of Herodotus of Halicarnassus, so that neither what has come to be from man in time might become faded.”