Reliability is concerned with the question in how far a measurement leads to the same result when the measurement is repeated

Validity concerns the question to what extent the measurement appropriately describes the concept one intends to describe.

The best way to think about it is the analogy of the target, which is explained in detail in: Trochim, W., Donnely, J.P., 2008. The research methods knowledge base, 3rd ed. Atomic Dog Publishing.

see also:

http://www.socialresearchmethods.net/kb/relandval.php

As above, reliability refers to the degree to which a measure is free from error and as a result provides consistent measurement.

Validity contains two elements, first, whether a measure accurately captures its target and second, judgments regarding whether or not it is appropriate to use a measure for a given purpose. This chapter gives a thorough review of validity: https://www.researchgate.net/publication/309994108_Psychometric_Validity_Establishing_the_Accuracy_and_Appropriateness_of_Psychometric_Measures 

Chapter Psychometric Validity: Establishing the Accuracy and Appropr...

Reliability deals with consistency and Validity with accuracy of research instrument..