In short, solid gold is absolutely real gold. The term 'solid' implies that there is gold alloy or material in the jewlery. It does not mean that it consists of exclusively gold. The purity of the alloy will determine the amount of gold in the jewelry.
How long does 14K solid gold last?
14K is meant to last a person's lifetime and beyond. This is why the metal is used for weddings bands and engagement rings.