Fidelity is a term that refers to faithfulness, and this is expected between a husband and wife because it is mentioned in the wedding vows taken. If you show fidelity then you are showing loyalty towards this person. Infidelity can destroy relationships and marriages, because it is a betrayal of trust and loyalty and it can be devastating for the person who is betrayed.
Fidelity is a virtue which should be frequently proved, but not always
Fidelity that is bought with money may be overcome with money
It's easier to be faithful to a restaurant than it is to a woman