The short answer:
18 refers to 18% chromium content, and the other number refers to the percentage of nickel content. There is no difference between 18/8 and 18/10. It's purely marketing. 18/0 however, has no nickel content, which means it won't keep its silver-like shine over the years.
The long answer:
The numbers 18/0, 18/8 and 18/10 refer to the percentages of chromium and nickel in the stainless steel alloy. The "18" refers to the chromium content, which gives flatware its rust-resistance properties, and the "8" or "10" refers to the nickel content, which gives it its silver-like shine and some rust-resistance. There is a lower quality flatware commonly available called 13/0 or 13 Chrome, which simply has 13% chromium content.
These numbers are merely "nicknames" for the lay person to use, and are only used for marketing efforts by flatware manufacturers. When a manufacturer purchases stainless steel from a steel mill, they purchase stainless steel Grade 304, which has a range of 18-20% chromium, and 8-10% nickel content. Grade 304 in flatware is usually at the lower end of that range. To keep the cost down, steel manufacturers will make grade 304 with 8.2% nickel, which clears the legal hurdle of calling it 18/10.
What does all this mean? It means that there is no difference between 18/8 and 18/10 stainless steel in flatware. The difference between the two is purely a marketing effort.
18/0 however, is a different story. It's made from the "Grade 400 series", which contains no nickel.
Keep in mind that these numbers do not refer to the weight of the stainless. If the weight is a concern to you, please ask your sales representative about the weight and feel of patterns you are interested in. As a general rule, the Silver Superstore does not sell stainless steel flatware that is flimsy, or bends easily.
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