What is often referred to as "normal" in the atmosphere and oceans is actually just an average of many variations including extremes over a long period of time.
Thus, the El Niņo phenomenon itself is not anything freakish or "abnormal." It is related to the natural ebb and flow of the trade winds over the tropical Pacific.
That, along with associated changes in atmospheric pressure across the Pacific, is known as the Southern Oscillation. The whole process is known as ENSO (El Niņo / Southern Oscillation). The opposite phenomenon to El Niņo is known as La Niņa.
During the mid to late 1990s, these phenomena garnered much attention throughout the globe. Increased scientific investigation and dramatic meteorological impact in various parts of the world brought this complex event into media focus.