Reaching for a metaphor To understand how DOP is calculated requires understanding statistics. If you just want to use it, and if you don't know statistics, just think about betting. Pick a sport, any sport. Whether it is pool, bowling, basketball, diving, the stock market, or whatever. There are difficult shots and easy shots.
Difficult things are riskier.
DOP is a rating of the difficulty of getting a good position out of a particular combination of GPS satellites. With low DOP, the position is probably closer to being right, but remember it's an estimate, not a guarantee.