Ы You say in world like (I)taly - Италия. Rusian ascent in English is read i like И, but English people say Ы, not i. But you say И in worlds like I (ea)t sandw(i)ch, (E)vening. My English it's not so good. I just study. But I try to explain what the difference in sound Ы and И. I hope what it's help somebody.
If it helps, typically, all nominative plurals end with 'ы'. HOWEVER, if a noun ends with one of these: г, к, х, ж, ч, ш, щ, your plural noun will end with an 'И' instead. That is the exception.
Examples: Кошка -- Кошки (cat female -- cats female) Банк -- Банки (bank -- banks) Нож -- Ножи (knife -- knives) Мост -- Мосты (bridge -- bridges) Пицца -- Пиццы (pizza -- pizzas)
и can mean "and" on its own. But both и and ы can be endings of words, as well as within words. One example is был: he was vs. бил: he beat. The pronunciation is what matters in order to tell the verbs apart, but usually context will help of knowing which verb is meant.
The sounds themselves are different, but similar. и softens the sound before it while ы is harder. There is some debate over these as whether they are distinct letters or just written differently but symbolize essentially the same sound, just one is palletized and one is not.
Grammatically speaking, one way to know which one is used is with the Spelling Rule: Never write the letter "Ы" after the letters 'Г, К, Х, Ж, Ч, Ш, Щ' instead use И.
In the case of tables, столы, it ends in ы because you add this for masculine nouns to make them plural if they end in a consonant. You use и to make the noun plural when the masculine singular noun ends in a ь or й.
For feminine nouns, however, you replace ь and я with и, but if the singular feminine noun ends in an 'а' you use Ы unless previous consonant is Г, К, Х, Ж, Ч, Ш, Щ. Then you replace with "и" to follow the Spelling Rule.
This sounds more confusing than it is. A chart would be simpler to look at: http://33.media.tumblr.com/5127b0b1aed2c5fd501d5ecc3a4747f3/tumblr_inline_mzgehrXN2T1qgkwq1.png.
I think the 'ы' sound actually exists in English at least in some dialects (maybe for example pronunciations of "new", the ones that aren't "noo") , just never on it's own (it doesn't in Russian either, though), there's always a consonant before it. It's somewhere between "u" (ooo) and "i" (eee), closer to the former. The speech synth is what it is, but if I confused 'ы' with something else it wouldn't be 'и'. They sound distinctly different to me.