how does iframe allow work code example

Example: iframe

<iframe id="inlineFrameExample"
    title="Inline Frame Example"
    width="300"
    height="200"
    src="https://www.openstreetmap.org/export/embed.html?bbox=-0.004017949104309083%2C51.47612752641776%2C0.00030577182769775396%2C51.478569861898606&layer=mapnik">
</iframe>