There is some quite good explanation in this thread on tc.

http://www.turkishclass.com/forumTitle_1729

I think the easiest way to differentiate between the two (at least for me) is to think of "konuþmak" as the verb "to talk" and "konuþma" as the noun "talking". It is actually called a verbal noun and can take suffixes that you would usually attach to a noun, for example "(y)ý" which puts this noun in the accusative case (makes it an object of the verb).

Konuþmak  is the  noun form  of  the  verb  "konuþ-". You need  to  learn  the  cases  to  understand  it  better.  There  is  some  info  below  for  gelmek  (to  come).  You  can  apply  it  to  konuþmak  yourself.

gelmek & gelme - they are both verbal nouns. We call them isim-fiil (noun form of a verb).

Different case suffixes make some difference in usage.

Nominative case (No suffix)
-mek form is used more.

gitmek istiyorum.
gitmek mi zor kalmak mý?

-e/-i cases and possessive suffixes
-me form is used almost always.

sana gelme-ye karar verdim.
sana gelme-yi düþünüyorum
sana gelme-m iyi olacak.

In theory -mek is possible but never used.

sana gelmeð-e karar verdim.
sana gelmeð-i düþünüyorum
sana gelmeð-im iyi olacak.

-de case
Both forms are possible and most of the times they are close in meaning.

eve gitmek-te fayda var.
eve gitme-de fayda var.

-den case
Both forms are possible but there may be difference.

eve gitmek-ten vazgeçtim.

eve gitmek-ten gitme-ye fark var.
eve gitme-den gitme-ye fark var.

with postpositions
-mek is used mostly. See nominative case also.

iþe gitmek için erken kalktým.