Learn Polish: W szpitalu pracują lekarze oraz pielęgniarki. - Doctors as well as nurses work in the hospital.

While i simply means "and", oraz translates closer to "as well as" or "and also". It is slightly more formal and is frequently used in Polish when joining two distinct categories of things or people—like lekarze (doctors) and pielęgniarki (nurses)—to give distinct, equal weight to both groups.

Szpital is a masculine noun. Why does it take an -u ending in the locative case (w szpitalu) instead of -e?

In the locative case (which is used after the preposition w to show location), masculine nouns usually take either an -e or -u ending. Because szpital ends in -l, which Polish grammar treats as a "soft" consonant, it must take the -u ending. You will see the exact same pattern with similar words, like hotel (w hotelu).

Why does the plural form of lekarz end in -e (lekarze)?

Lekarz (doctor) is a "masculine personal" noun, meaning it describes a male or mixed-gender group of people. For these nouns, the nominative plural ending depends on the final consonant. Words ending in -rz (as well as -cz and -sz) take the -e ending to form the plural, which is why it becomes lekarze.