When people say women cheat in marriages/relationships because of "boredom", what exactly do they mean by "boredom"?

The term "boredom" is very vague when used in this sense. From what I understand, women probably cheat when they don't get sexual gratification from a relationship, but I doubt that's the whole story.

Updates
8 mo
Please be specific, otherwise you won't provide much clarification.
When people say women cheat in marriages/relationships because of "boredom", what exactly do they mean by "boredom"?
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