Tengo una bolsa.
English: I have a bag.
Articles are small words before nouns. In Spanish, they show gender (masculine/feminine) and number (singular/plural), and signal if a noun is specific or general.
Use 'un/una' for one non-specific item, 'el/la' for a known or specific item.
Tengo una bolsa.
English: I have a bag.
Ella es una artista.
English: She is an artist.
La bolsa está en la mesa.
English: The bag is on the table.
Él quiere un boleto.
English: He wants a ticket.