what the underlined letters mean?
im a beginner Russian learner and I want to know what is the function of the underlines letters that are present in most phrases
Do you mean in Russian handwritten cursive or some fancier, italicized fonts? In those cases you will sometimes see ш with a line under it to distinguish it from ии, just as you will sometimes see a line over т. I can't think of any other places you will see lines under letters. In some fonts I suppose the little tail on ц and щ might be exaggerated too.
http://www.russianlessons.net/lessons/lesson2_main.php some of the Russian words have a underlining in some letters like один (и is underlined)