Well, theoretically speaking there are lots of different sounds in Russian depending on their position or environmemt. In unstressed syllables O and A sounds the same (except some foreign words like радио or unstressed prepositions like возле). И and Э also merge and any distinction is lost.
In practice unstressed O/A sound is "something like A" and unstressed Э/И vowel is "something like И", at least in standard pronunciation. Native Russian speakers perceive unstressed E as И and О as А, though strictly speaking the sounds are a little different and less clear (only they are the same phoneme and don't distinguish the words, though MAY be completely different sounds in some other language). Also, unstressed Я, as far as I can tell, becomes йи (word initial, like "ягу`ар") or "и" (after a consonant, like "поня`ла"). Unstressed А becomes Ы after Ж/Ш ("жал`еть" /жыл'эт'/). There may be deviations for some accents. Besides, older theatrical pronunciation (like, 50 years ago) encouraged actors to "brighten" the sound by not completely reducing unstressed Е to И, leaving the vowel still somewhats E-like. That's not how people speak in reality, and certainly not today.