Logical validity is a technical term used to describe formulae of formal logic. A logically valid formula is one that will always have a true conclusion if it has true premises. For example, the following arguments both represent valid logical formulae.
Now, although the first argument is clearly true, the second is clearly false. However, they are both valid, as, if the premises of the second were true, then the conclusion would also be true. It is not necessary for a valid argument to be a true one; cases where a valid argument is also true are called sound arguments.