Russian has a number of grammatical forms that are derived from verbs and are called deverbal forms. The present deverbal adverb is derived from the present stem of Imperfective verbs and it is used to form adverbial phrases with the general meaning 'while -ing', e.g.
Читђя газљту, ћн љл колбасџ. While reading the newspaper, he ate sausage.
The ending of this form is -я (spelled -а after ч щ ш ж, e.g. ложђсь). It is stressed if the non-past pattern is E or M (говорї, выходї), unstressed if S (вќдя). Some verbs don't have a present deverbal adverb; check The Russian Dictionary Tree or 5000 Russian Words.
The present deverbal adverb occurs more frequently in written style than in spoken style, though it is often used in expressions that correspond to English 'without -ing', as in:
Ћн стоїл, ничегћ не говорї. He stood there without saying anything.
It occurs in some set expressions:
Чљстно говорї, ї не знђю. Frankly (speaking), I don't know.
Ї никогдђ нљ бІл в Россќи, не говорї ужљ о Москвљ. I've never been to Russia, to say nothing of Moscow (not speaking of Moscow).