Learn Portuguese (Portugal): A loja vende pão.

In Portuguese, all nouns have a gender. The word loja (shop) is feminine, so it must be paired with the feminine word for 'the', which is a. If the noun were masculine, we would use o.

Why does the verb end in -e here (vende)?

Vende comes from the regular verb vender (to sell). Because a loja (the shop) acts as an 'it' (third-person singular), we drop the -er ending and add -e. If you were saying 'I sell', it would be vendo.

Why is there no article like o or um before pão?

Just like in English, when you are talking about an uncountable noun in a general sense ('sells bread', rather than 'sells the bread'), you can leave out the article in Portuguese.

What does the squiggly line over the 'a' in pão mean?

That mark is called a tilde, and it tells you to make a nasal sound. The ão combination sounds a bit like the English word 'ow' said while pushing the air through your nose.