What is 'IV range' in relation to IVs? Is one more important than the other?

I am attempting to catch strong pokemon in Pokemon Go. I have heard that a pokemon with max IV is strong. I know what IVs are, but what is IV range? Is it necessary?

Solution 1:

Based on the stats a pokémon has, people try to predict what IV's the pokémon has. The higher the IV's, the higher a specific stat of the pokémon can become. If the level of the pokémon (or the stats) is still low, it is mathematically impossible to calculate the correct value exactly. At lower levels, the same IV can generate several possible values. An IV range is the range of possible IV values the pokémon has for a specific stat.