Not to be confused with Hit%
Hit Rate is a measurement of how good a character is at striking a target. It is not a percentage, although it is often shown as such. This stems from the fact that the random numbers used for hitting are not single numbers, but averaged pairs. This weights the result toward the center, making 50 far more common than 1 or 100, for example. The result is that, if given a 'percentage' of 80%, your actual chance is higher than that; it's more like 90%.
Hit Rate most often depends on the inherent Accuracy of the weapon being used by the character, and the character's Skill. This is in fact the case for almost every Fire Emblem game the only exception being Fire Emblem: Ankoku Ryū to Hikari no Tsurugi, where a character's Hit Rate with Magic relies on the magic's accuracy alone. A character's Hit Rate is used in conjunction with their opponent's Evade in order to determine the character's Accuracy in a battle.