Infidelity is a relationship with other people who are not his partner. Infidelity can be done by men or women. The form of infidelity can vary.
Connecting with people outside the couple may be in physical and non-physical form. Physical form of kissing, handrails, hugs and intercourse. Non-physical form of falling in love, glance, talk, or relate through medsos
I think narrowing is a dishonest act against a spouse and betrayed loyalty to a spouse. The shape can be various.