Learn Russian: Мы должны встретить нашего дядю на станции.

Дядя (uncle) is a special masculine noun. Because it ends in -я, its own endings change like a feminine noun (the nominative -я becomes the accusative -ю). However, because an uncle is a male person, any adjectives or pronouns describing him must remain masculine. Since he is an animate direct object (a living person) in the accusative case, the masculine pronoun наш takes the animate ending -его, giving us нашего дядю.

Why use the perfective verb встретить (to meet) here instead of the imperfective встречать?

We use the perfective встретить because this refers to a single, specific event with a clear result: successfully picking him up at the station this one time. If you were talking about a repeated habit, like 'We must meet our uncle at the station every Friday,' you would use the imperfective встречать.

Why does на станции end in -ии instead of the usual prepositional ending -е?

The dictionary form of the word for 'station' is станция. Feminine nouns that end in -ия are a minor exception in the prepositional case. Instead of taking the standard -е, their ending changes to -ии.

How does this relate to the lesson's focus on arrival verbs like приехать?