Learn Hardcore German: Wir essen Pizza am Abend.

am Abend literally means at the evening but is used to express in the evening. It comes from the preposition an combined with the dative article dem (an + dem = am). German often uses am + noun when talking about parts of the day.

Can I say abends instead of am Abend?

Yes. abends is an adverb meaning in the evening(s) for habitual actions. am Abend is used for a specific or general time (e.g. tonight).
• Wir essen Pizza am Abend. (We are eating pizza this evening)
• Wir essen abends oft Pizza. (We often eat pizza in the evenings)

Why is there no article before Pizza?

When talking about food in general or an unspecified amount, German omits the article. Here Pizza is treated as a mass noun. If you mean one specific pizza, you would say:
• Wir essen eine Pizza.
• Wir essen die Pizza.

Which case is Pizza in and how can I tell?

Pizza is the direct object of essen, so it is in the accusative case. The feminine noun die Pizza has the same form in nominative and accusative, so it remains Pizza here.

Why is the word order Wir essen Pizza am Abend and not Wir am Abend essen Pizza?

German main clauses follow the Verb-Second rule: the finite verb (essen) must be in the second position. With Wir first, essen is second, followed by object and time. If you move the time phrase to the front, invert subject and verb:
• Am Abend essen wir Pizza.

Why is Abend capitalized but am is not?

All German nouns are capitalized, so Abend starts with a capital letter. am is a contraction of the preposition an and the article dem, neither of which is a noun, so am stays lowercase.

Can the present tense Wir essen Pizza am Abend refer to a future plan?

Yes. In German, the present tense can express future events when there is a time indicator. Wir essen Pizza am Abend can mean We are going to eat pizza in the evening.