Explain what the difference between latent and masked defects is?

Latent defect is a failure that is still hidden as the set of condition were never met that can uncover a defect.
Masked defect is a defect that has not yet caused because another defect has prevented the area of code from being executed so that masked defect can be found.
When set of condition or scenario are executed, latent defect will be discovered. Masked defect can be found once the defect preventing to execute area of application is resolved.