The difference between Affix and Postfix

When used as nouns, affix means that which is affixed, whereas postfix means suffix.

When used as verbs, affix means to attach, whereas postfix means to suffix.

check bellow for the other definitions of Affix and Postfix

Affix as a noun:

That which is affixed; an appendage.
Affix as a noun (linguistic morphology):

A bound morpheme added to the word's stem's end.
Affix as a noun (linguistic morphology):

A bound morpheme added to a word's stem; the term comprises prefixes, suffixes, infixes, circumfixes, and suprafixes.
Affix as a noun (mathematics):

The complex number a+bi associated with the point in the Gauss plane with coordinates (a,b).
Affix as a noun (decorative art):

Any small feature, as a figure, a flower, or the like, added for ornament to a vessel or other utensil, to an architectural feature.

Affix as a verb (transitive):

To attach.

Examples:

"to affix a stigma to a person; to affix ridicule or blame to somebody"
Affix as a verb (transitive):

To subjoin, annex, or add at the close or end; to append to.

Examples:

"to affix a syllable to a word; to affix a seal to an instrument; to affix one's name to a writing"
Affix as a verb (transitive):

To fix or fasten figuratively; with on or upon.

Examples:

"eyes affixed upon the ground"

"rfquotek Edmund Spenser"

Postfix as a noun (chiefly, computing):

Suffix.

Examples:

"rfquotek Parkhurst"