What does a "smart casual" dress code actually mean?

I am glad I found this topic because my husband thought that smart casual just meant jeans with a collared polo style shirt as long as it was collared it was considered smart casual in his mind lol, now I can tell him he was wrong but it's ok because he listened to me in the end and is wearing dress pants with a long sleeved collared shirt without a tie and some nice business style black shoes. I am wearing a knee length dress with buttons down the front accessorised with a brown "rope" style belt and some wedge heel styled shoes to match in colour. The children are wearing casual pants (not denim but not formal) with a collared short sleeved shirt. I hope I got this right!

Something smart but not too formal. For example, ladies can wear a pair of trouser/skirt with a nice shirt, but not necessarily with the jacket. Likewise guys could wear trousers with a shirt and tie only (without jacket).

You are going to an informal dinner with friends in an upscale restaurant. If male, you are wearing dress trousers (or even crisp jeans*), a long-sleeve shirt, maybe a tie, leather loafers or dressy slip-on's, patterned socks or solid-colored dress socks, a tipped belt, and you may or may not wear a sport coat. You are dressed in the Smart Casual category.

If female, you are wearing slacks, crisp jeans, or a skirt (long or short), a blouse or turtleneck, a fashionable belt, a jacket, a vest, or a sweater coordinated to your outfit, hosiery or socks with boots, flats (leather, suede, or fabric) or mid-heel shoes. You are also wearing jewelry, such as earrings that complement your overall outfit, at least. You are dressed in the Smart Casual category. Again, if you are wearing jeans, wearing a jacket upgrades you to Smart Casual. This category demands a pulled-together, harmonious, complete look with colors, fabrics, shoes, and accessories, for both men and women.

*If you are wearing crisp jeans, you must wear a sport coat for Smart Casual.

Smart casual is the kind of clothing you might find somebody wearing in the club house of a private golf club... for example, polo shirt, slacks and casual shoes.

It may differ between countries, and even towns and other places (like which restaurant it is), and at work even between jobs and employers.