An iFrame is just a frame window embedded in a regular HTML page
instead of in a Frameset. You can put it in the page any way you
like. Bare naked, in a Table cell, or in a Layer.

It has all the characteristics of a regular frameset.

It adds functionality to a page.

You can make it ugly or you can make it beautiful. You can have
borders and scrollbars, or not. It's all up to you. How you design in
Frames is similar to how you design an HTML page, or how you decorate
your house. For example, I once sold vinyl siding to a woman in
Richmond, California, who lived in a bright green house with orange
trim. It stuck out like an abnormal growth in the neighborhood. When
it came down to choosing the colors, I suggested a nice white with a
light gray or blue trim. She picked green siding with orange-painted
trim, and was a bit disappointed that we didn't have a hideous green
siding like the color she had painted her house.