Manual-priority autofocus means the lens can autofocus normally, but you can override it by turning the focus ring without switching fully into manual mode. On Nikon lenses this is typically the M/A setting.

In practice, it lets you:

• use autofocus as usual
• fine-tune focus manually at any time
• on some lenses, interrupt autofocus immediately and take over manually

This is useful when autofocus gets close but you want to make a small adjustment yourself.

The key difference from many older or simpler AF lenses is that those may not allow safe manual turning of the focus ring while AF is engaged, because doing so could stress or damage the AF mechanism. With manual-priority/full-time manual override designs, the lens is built to allow that manual adjustment safely.

So it’s basically autofocus with instant manual override, rather than a separate all-manual mode.