Once upon a time Nokia was a giant in the industry. They towered over everyone even Apple and held the market with their own OS Symbian for a number of years.
Unfortunately as the rest of the world broke into Android and iOS Symbian was quickly forgotten even though it is one of the founders of the smartphone era. Nokia was also no slouch at developing hardware either. They are the holders of a large number of patents (their own inventions too). Still despite all of this Nokia could not hold onto the crown. After a few years trying to make Symbian more relevant they have dropped several rungs in the ladder and now are partnered up with Microsoft as the premier partner for their Windows Phone platform.