What is a "Raw" Coin?

By GovMint :

A "raw" coin is a term used in numismatics to describe a coin that has not been certified and encapsulated by a third-party grading service like Numismatic Guaranty Company (NGC) or Professional Coin Grading Service (PCGS). Raw coins, also referred to as ungraded coins, are sold in their natural state, as issued by the mint. They will not arrive with any numerical or adjectival grade affixed to them and are usually packaged in a cap or a flip versus being sonically sealed in a protective slab like a graded coin would be. 

Sources Used:

 https://www.royalmint.com/stories/sovereign/story-of-the-sovereign/