The same as between sz and ś, or cz and ć, or dż and dź.
ż, sz, cz, dż are retroflex: the tip of the tongue touches (or almost touches) just behind the alveolar ridge. If you speak Russian, it's like ш/ж. If you speak Chinese, it's almost (but not quite) like sh/ch/zh/r. If you speak Swedish, it's almost like rs in most dialects.
ź, ś, ć, dź are alveopalatal: the middle of the tongue touches (or almost touches) a bit before the middle of the hard palate. A similar position to the one used with Polish j/English y. If you speak Russian, it's almost like ч/щ. If you speak Chinese, it's like x/q/j. If you speak Japanese, it's like ch/sh/j.
In contrast, English sh, ch, j are alveolar: the point before the middle of the tongue touches (or almost touches) the alveolar ridge. This is also the sound of German sch, French ch/j, Ukrainian ш/ч/ж and so on. For Polish speakers, those English consonants sound in between retroflex and alveopalatal, although the tongue position doesn't reflect that. When a Polish speaker wants to pretend to speak Polish with a foreign accent, switching to those consonants is a good start – conversely, those consonants are an almost sure tell you're a foreign speaker.
You can find sound clips online, on Wikipedia, Forvo or Youtube, or you can use Google Translate's or Ivona's online text-to-speech tools to learn to hear the difference.
So do you think it's accurate to say that we don't need to worry about these subtle differences right now?
After all, speakers of a new language almost always have an accent, at least in the beginning, right?
Maybe that final perfection can be learned from an accent coach (or simply talking to native speakers)?
As a polish native speaker I can say that to find similar sounds in English will be very hard as both z sounds r very different. The closest you can compare ż with that it has a heavy sound comparing to the other z. It will produce a sh sounds from a world like : SHap but don't say the sh the way you would with your normal accent. the sh sound is sharp and your tounge touches the top of your mouth while your top and bottom teeth are touching. WHILE the other ź has a sounds similar to the American way of pronouncing zebra. It kinda of goes of with a zii but not fully and your mouth is in a shape as if you would be smiling. But its better to listen to someone pronounce the ź as its hard to replicate with a English word. Hope this helps.
Ź is not źebra in English! That would be zhebra. In Polish letters it's more like zjibra. Z is the same for Polish and English. Ź is "zh" in English. As far as Ż, for an English speaker, the tongue goes in the position for English R but instead says "zh"/Ź in that position, and you get Ż/"rz"
Ohh very much thanks for the explanation and the link even though i find it a bit hard to translate the english grammar to my own lang (greek) so to understand the full meaning of the cases listed in the link. Sadly there is not direct Greek to polish lesson in duolingo and i took the english-polish one :(
It includes tenses. So in polish you get a word and its at its most basic form such as water with is woda. But when you put it in a sentence with I'm drinking, your doing the action right now, in the moment. It turns woda to fit into the tense and become wode.
Same goes with other words like foot which is stopa. Both water and foot end with a because their not inserted into a sense yet. But this word then turns to eg You stepped on my foot! "Stanelas na moja stope!" It will not be - "stanelas na moja STOPA.
I have always been bad at phonetics, but Wikipedia states that Polish "e" is an open-mid unrounded front vowel, so \ɛ.
Technically here you have "ę". About ę Wikipedia says: "It is most commonly pronounced as /ɛw̃/, /ɛn/, /ɛm/, or /ɛ/, depending on the context." It's generally a nasalized "e". Something similar to Spanish for "Europa". When it's the final sound of the word, most people pronounce it the same as normal "e" or nasalize it just a bit.
That's not incorrect, but it's based on context and doesn't directly translate. "A water" usually means a bottle of water or a glass of water. In Polish that would likely be "jedną wodę" or "butelkę wody" or the like. Water is a mass noun like sand or rice. You usually don't say "a sand" or "a rice," again unless you're ordering one portion of rice at a restaurant.