Every weapon skin, knife and pair of gloves in CS2 carries a float value, sometimes called the wear rating. It is a decimal between 0.00 and 1.00. Lower means cleaner, higher means more worn. The float is rolled when the item is created, whether by a case, a drop or a trade-up, and it never changes afterwards, no matter how much you use the item.
The float decides the wear tier shown on the item. Factory New covers 0.00 to 0.07, Minimal Wear 0.07 to 0.15, Field-Tested 0.15 to 0.38, Well-Worn 0.38 to 0.45 and Battle-Scarred 0.45 to 1.00. The game only displays the tier; to see the exact float you inspect the item in game or paste its inspect link into a float checker.
Why does the exact float matter if the tier is the same?
Because prices follow the number, not just the label. Buyers pay more for a 0.01 Factory New than a 0.06 Factory New, and collectors pay large premiums for floats near 0.00 or near 1.00. Inside wide tiers like Field-Tested the low end and the high end can look like different skins. Two listings with the same name and tier can differ a lot in price for this reason, and float is usually the explanation.
Floats are not spread evenly. More items land at low floats than high ones, which is part of why Battle-Scarred copies near 1.00 are rare even though the tier is wide.
What is the difference between float value and float cap?
The float value is the number a single item has. The float cap is the range a finish allows. Some finishes cannot go below or above a certain float, so their copies only exist in some tiers. A finish with a cap of 0.10 to 0.70 will never be a true 0.00 Factory New, and it will never reach 1.00. Knowing both numbers is how traders judge whether a float is rare for that skin or just ordinary.
In trade-ups the output float comes from the inputs. The average of the normalized input floats is mapped onto the output skin's cap range, so input floats decide the wear of the result.