Learn Croatian: Kruh je doma. - The bread is at home.

Look at the last letter! Kruh ends in a consonant (h). In Croatian, regular nouns that end in a consonant in the nominative singular (the basic dictionary form) are masculine. If it ended in -a, it would usually be feminine, and if it ended in -o or -e, it would be neuter.

The English translation says "The bread", but there is no word for "the" here. Why?

Croatian doesn't have definite or indefinite articles like "the", "a", or "an". A simple noun like kruh can mean "bread", "a bread", or "the bread". You just rely on the context of the conversation to know which one makes the most sense in English.

Why does this sentence use doma for "at home" instead of a form of kuća?

Kuća means a physical "house". Doma is a very common adverb meaning "at home" (it comes from the noun dom, meaning "home"). Just like in English, saying "the bread is at home" (kruh je doma) is a natural way to express location without talking about the physical building.

Could I change the word order and say Je kruh doma?

No, you can't start this sentence with je. The word je (is) is a special unstressed word called an enclitic. A major rule in Croatian is that enclitics almost always have to sit in the second position in a sentence. Putting je right at the beginning breaks this rule.