Learn Spanish (Latin America): Fuimos a una velada espléndida anoche.

You know it means "we went" (from the verb ir) because it is followed by the preposition a (to) and a destination. When fuimos comes from the verb ser (to be), it is usually followed by an adjective or a noun to describe a characteristic or identity, not a destination.

What exactly is una velada?

It translates to an evening party, gathering, or soiree. The word shares a root with vela (candle) and velar (to stay awake), which makes sense since it refers to a social event that lasts into the evening or night.

I sometimes try to translate "last night" as la noche pasada. Why is anoche used here?

While la noche pasada makes literal sense, anoche is the dedicated, everyday vocabulary word used in Spanish for "last night". Native speakers almost universally use anoche, so using it makes your Spanish sound much more natural and fluent.

Why is the word order velada espléndida instead of espléndida velada?

In Spanish, descriptive adjectives typically follow the noun they modify. Placing espléndida after velada is the standard, everyday way to describe what kind of evening it was without sounding overly poetic or dramatic.