Contrast with technology. A check often made is to have two or more people independently observe and report what they saw, to try to obtain interobserver corroboration. Nonscientific instruments are often both inaccurate and imprecise, e.g., the gas gage on a car. Valid measures should correlate with other measures of the same concept and with outcomes expected of the concept. E.g., how long one can balance a ball on one's nose will not correlate with other measures of intelligence, nor predict success in school, etc.
Reliability is the consistency of a measure.
If confirmed , then you found support for theory.