Learn Arabic (Modern Standard): عنده حقيبة بنية.

Arabic doesn't have a direct verb for 'to have'. Instead, it uses a preposition like عند (meaning 'with' or 'at') plus an attached pronoun. Here, عند is combined with the pronoun suffix ـه (his/him), literally translating to 'at him is'.

Why is the word order حقيبة بنية instead of the other way around?

In Arabic, the adjective always comes after the noun it describes. So instead of 'brown bag' like in English, you say 'bag brown' (حقيبة بنية).

Why does the word for brown, بنية, end with the letter taa marbuuTa (ة)?

Adjectives must match their nouns in gender. The word for bag, حقيبة, is feminine, which we can tell because it ends in the letter taa marbuuTa (ة). Therefore, the masculine adjective for brown, بني, gets a taa marbuuTa added to the end to become the feminine بنية.

Is there a specific word for 'a' in this sentence?

No, Arabic does not have an indefinite article like 'a' or 'an'. If a noun doesn't have the definite article prefix الـ (the) attached to it, it is usually understood as indefinite. So, حقيبة simply translates to 'a bag'.