A mirror or (almost) any other well polished material, exhibit specular reflection, in which the law of reflection is observed (angle of incidence equals angle of reflection).

Virtually all materials can give specular reflection, provided that their surface can be polished to eliminate irregularities comparable with light wavelength (a fraction of a micrometer). (Wikipedia)

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A white wall has surface irregularities larger than visible light wavelength, such that reflection occurs in all directions so no image is formed. But still a white wall appears as white because because it saturates the eye with all the wavelengths reflected from it.

A mirror or (almost) any other well polished material, exhibit specular reflection, in which the law of reflection is observed (angle of incidence equals angle of reflection).

Virtually all materials can give specular reflection, provided that their surface can be polished to eliminate irregularities comparable with light wavelength (a fraction of a micrometer). (Wikipedia)

(source)

A white wall has surface irregularities larger than visible light wavelength, such that reflection occurs in all directions so no image is formed. But still a white wall appears as white because it saturates the eye with all the wavelengths reflected from it.