@Troy read this since you are confusing a valid and true conclusion.
Premise: all horses are brown
Premise: X is a horse
Conclusion: from premise 1 and 2 follows that X is brown
However, suppose that X in fact isn't brown, but white (meaning that either X isn't a horse - premise 2 is false -, or not all horses are brown - premise 1 is false).
The reasoning leading to the conclusion is logically valid, it's a valid reasoning, but the conclusion is not true, because we started with false premises