Learn Polish: W każdym mieście jest rynek. - In every town there is a market square.

After the preposition w (in), we need the Locative case to describe a location. For neuter nouns ending in -o like miasto, the Locative ending is -e. Adding this ending triggers two internal changes: the vowel a shifts to e, and the hard consonant cluster st softens to ść, resulting in mieście.

Does rynek just mean a market where you buy food?

Not usually. In the context of a Polish town, the rynek is the central town square, which is often historic and surrounded by colorful buildings or a town hall. If you want to talk about a standard farmers' market for buying produce, you would typically use the word targ or bazar.

Why doesn't the sentence say tam jest to mean 'there is'?

Polish doesn't use a dummy word like 'there' to express existence. The verb być (here as jest) is enough on its own. When you put the location first (W każdym mieście) and follow it with jest, it naturally translates to 'In every town there is'.

Why does każdy end in -ym here?