The first thing to understand is what we mean when we speak about "Pure Gold" or the various Karats of Gold.
Pure Gold is 100% Gold, unmixed with any other element, and is also commonly referred to as 24 Karat Gold (or 24K Gold).

Pure Gold is beautiful and rare.  However, it is also relatively soft.  In order to make jewelry that is durable enough to be worn we must mix Gold with other metals such as Silver & Copper.  The Karat number refers to what percentage of the metal is Gold and what percentage is other metals. 
​The higher Karat number means the greater percentage of the metal is Gold.  

The most common Karat for Gold is 14K.  It provides a durable piece of jewelry at a reasonable price.  The 10K Gold offers a greater affordability with a lower price and a high resistance to scratches or being misshapen.  The drawback for the lower Karat is the 10K is more brittle than the others.  The 10K ring is less likely to bend, but more likely to break into pieces.  The 18K is typically more expensive than the 14K.  It is heavier and still maintains a durability and resistance to scratches.  It is an excellent choice for fine jewelry pieces if your budget will allow for it.  The 22K and 24K are quite soft and the most expensive.  A 24K ring can be reshaped by simply applying pressure with your bare fingers. (It realy is that soft).

Another thing to consider is how solid your jewelry is.  The highest quality jewelry will be Solid Gold.