Snoke is a very mysterious and intriguing figure who, according to the novelization, witnessed the rise and fall of the Empire. Where was Snoke during this time? Was he someone Palpatine was aware of, or was he lurking in the shadows, waiting for his time to rise to power?
His disfigured visage shows that he received massive damage at some point. This has led many to believe that he could be Darth Plagueis, the master of Palpatine who experimented with cheating death and creating life (it is hinted by Palpatine that Plagueis was the one who created Anakin). Palpatine revealed to Anakin that he killed his master in his sleep, but it is possible that Plagueis somehow survived using secret knowledge to preserve his life, then waited for Palpatine to make a mistake so he could once again seize power for himself.
Another possibility is that he was an Inquisitor or dark side adviser to Palpatine. In the novel Aftermath, a character called Tashu, one of Palpatine’s non-Force-sensitive advisers, spoke of Palpatine funding research in the Unknown Regions beyond the known galaxy. This is where Palpatine believed the dark side originated. Tashu believed that the Imperial remnant should flee there to seek the source of the dark side as their savior. It makes sense that Palpatine would utilize Force-sensitives for this purpose. Snoke could have been one of these individuals and was already there when the Imperial remnant fled into the Unknown Regions to form the First Order. The remnant would likely turn to a Force user to rebuild their power.
According to the Visual Dictionary and the novelization, Snoke sees Kylo as the perfect embodiment of the Force, having familial connections with both the dark side and the light. This could be a clue that the Force philosophy they follow is not that of the Sith, but something newer, or older.
Until next time: May the Force be with you. Always.