These are components of a Windows format PostScript Type 1 font. Some of them have also been of use on other platforms.

.afm = Contains spacing and kerning info for a font. Not used normally in Windows, except in special situations.
.inf = An informational file used by some older MS-DOS programs.
.pfm A file similar to the .afm, required by Adobe Type Manager (ATM) for Windows.
.pfb The file that contains the actual font outlines for use with Windows.

Only the second two are normally needed to use a Type 1 font on Windows.

Windows PostScript Type 1 fonts have not been supported by any version of Mac OS (or even the Mac version of ATM). You will need some sort of conversion utility or font editor to make them usable on a Mac.

Note that:
1) It's possible that these are illegal copies of fonts.
2) Quite often conversion from one format to another is
not allowed in a font's license. On the other hand, I'm
of the opinion that if a font is legally owned and the
resultant conversion stays on the hard disk of the font's
owner, it's OK.

hhp

Mark: ‘Windows PostScript Type 1 fonts have not been supported by any version of Mac OS [...]’
 
The Adobe font engine supports PS Type1 for Windows also on the Mac though. Dropping the files in the applicable fonts folder should do the trick for the Adobe apps.
 
Hrant: ‘I'm of the opinion that if a font is legally owned and the resultant conversion stays on the hard disk of the font's owner, it's OK.’
 
We will ad a special ‘Hrant clause’ to our EULA then ;-)

The Adobe font engine supports PS Type1 for Windows also on the Mac though. Dropping the files in the applicable fonts folder should do the trick for the Adobe apps.

Interesting. I didn't know that.

Frank, it's in there already, just invisible. :-)
Being a formal thing, a EULA has to be much
more draconian than the people it serves.
Reasonably and thankfully, as far as I'm aware
no font house will go hunting down people who
convert font formats internally.

hhp