Learn French: Nous avons exploré les canaux locaux.

The singular form is un canal. In French, when a noun ends in -al, its plural form usually drops the -al and adds -aux. Therefore, canal becomes canaux.

Why does the adjective locaux also end in -aux?

Adjectives must match the noun they describe. The singular masculine adjective is local. Because canaux is a masculine plural noun, the adjective must also be masculine plural. Just like nouns, masculine adjectives ending in -al change to -aux in the plural.

Why is it canaux locaux and not locaux canaux?

In French, most adjectives are placed after the noun they describe. Because local categorizes the noun, it goes after it, giving us les canaux locaux (the canals local).

What tense is avons exploré?

This is the passé composé, the most common past tense in French for completed actions. It is built using a helper verb, in this case avons (we have), and the past participle of the main verb, which is exploré (explored).