Learn Polish: Zawsze dzwonię, kiedy wracam do domu. - I always call when I come back home.

In Polish, the verbs dzwonię (I call) and wracam (I return) already have endings that tell us exactly who is doing the action. The -ę in dzwonię and -am in wracam mean "I", so the pronoun ja (I) is usually dropped unless you want to emphasize it.

Both dzwonię and wracam mean "I do something", but they have different endings (-ę vs -am). Why?

Polish verbs belong to different conjugation groups based on their infinitive (dictionary) forms. Dzwonić (to call) belongs to a group that takes the -ę ending for "I", while wracać (to return) belongs to a group that takes the -am ending. When you learn a new Polish verb, you will also learn which ending pattern it follows.

Why is there a comma before kiedy? We wouldn't use one in English here.

Polish punctuation rules are very strict about joining two parts of a sentence that each have their own verb. You must almost always put a comma before connecting words like kiedy (when), że (that), or bo (because), even if it feels completely unnatural for an English speaker.

Why does the sentence use do domu instead of just dom or w domu?