Reliability is something that can be reasonably assured of performing or functioning as it is intended or a source of reference. Validity means that it an authentic or actual product or service or document and not a forged or faked instrument to be relied upon. So something can be reliable but not valid just as something could be valid but not reliable.
Valid is when your method answers you aim/hypothesis. Reliable is when your results are assured by doing repeats, choosing an appropriate range of independent variable.