Learn German: Wir besuchen die Großeltern am Wochenende. - We are visiting the grandparents at the weekend.

German doesn't have a continuous tense like the English "-ing" form. You use the simple present tense (besuchen) for both "we visit" and "we are visiting". The context tells you which one is meant.

Where does the word am come from in am Wochenende?

am is a contraction of the preposition an (at/on) and the dative article dem. When talking about days of the week or the weekend, German uses an. Because das Wochenende is a neuter noun, its article changes to dem in the dative case to express a specific point in time answering the question "when?". an + dem combines into am.

Could I put am Wochenende somewhere else in the sentence?

Yes! German word order is flexible as long as the conjugated verb stays in the second position. You could say Am Wochenende besuchen wir die Großeltern to put focus on the time. Notice how besuchen stays in the second spot, so the subject wir has to move behind it. You could also put the time before the object: Wir besuchen am Wochenende die Großeltern.

What case is die Großeltern in here?