For more articles on the Russian alphabet , click here.
, when put after a consonant, acts like a "silent back vowel" that separates a succeeding iotated vowel from the consonant, making that sound with a distinct /j/ glide. Today it is used mostly to separate a prefix from the following root. Its original pronunciation, lost by 1400 at the latest, was that of a very short middle schwa-like sound,
acts like a "silent front vowel" and indicates that the preceding consonant is palatalized. This is important as palatalization is phonemic in Russian. For example, 
('brother') contrasts with 
('to take'). The original pronunciation of the soft sign, lost by 1400 at the latest, was that of a very short fronted reduced vowel 
. There are still some remains of this ancient reading in modern Russian, in the co-existing versions of the same name, read differently, such as in 
(Mary).
For more articles on the Russian alphabet , click here.
http://russian-alphabet.com/vocalized.htm