El concierto fue genial.

Fue is the third-person singular preterite form of ser. Here it means was.

So:

• el concierto = the concert
• fue = was
• genial = great / fantastic

A small warning: fue can also come from ir and mean went, but in this sentence it clearly comes from ser because it is describing the concert.

Spanish often uses the preterite (fue) for a completed event seen as a whole.

A concert is a finished event, so El concierto fue genial sounds very natural: you are giving an overall judgment about it.

Era is the imperfect, which is more often used for:

• background description
• repeated situations
• ongoing states in the past

So:

• El concierto fue genial = The concert was great.
  (a complete past event)

Using era here would usually sound less natural unless you are describing it in a different kind of context.

Yes. El concierto estuvo genial is also very common and natural.

Both are possible, but there is a slight nuance:

• fue genial often gives a general overall evaluation of the event
• estuvo genial often focuses on how it turned out or how the experience was

In everyday speech, especially informally, many speakers use both very naturally.

El is the masculine singular definite article, meaning the.

So el concierto means the concert.

Spanish uses articles very often, and here it is referring to a specific concert already known from the context.

Compare:

• El concierto fue genial = The concert was great.
• Un concierto fue genial would mean A concert was great, which usually sounds less natural unless you are contrasting it with others.

Nouns in Spanish have grammatical gender, and concierto is a masculine noun.

That is why it takes:

• el concierto
• not la concierto

There is no deep logical reason you can always predict; gender is part of the noun and must be learned with it. A good habit is to learn nouns together with their article:

• el concierto
• la canción
• el festival

Yes, it does agree, but genial is one of those adjectives that has the same form for masculine and feminine singular.

So you get:

• el concierto fue genial
• la idea fue genial

The adjective only changes in the plural:

• los conciertos fueron geniales
• las ideas fueron geniales

So genial does agree, but you only see a visible change in number, not in gender.

Because here genial is not directly describing the noun inside the noun phrase. It is part of the structure with ser:

• El concierto fue genial

This is like saying:

• subject: El concierto
• verb: fue
• complement: genial

If you put the adjective directly with the noun, you get:

• un concierto genial = a great concert

So:

• El concierto fue genial = The concert was great.
• Fuimos a un concierto genial = We went to a great concert.

In most of Spain, concierto is pronounced approximately:

kon-THYER-to

Key points:

• c before i is usually pronounced like th in think in most of Spain
• ie forms a diphthong, something like yer
• the r is a tapped Spanish r, not a strong English r

A rough pronunciation guide for Spain would be:

el kon-THYER-to FWEH heh-NYAL

In Spain, genial is roughly:

heh-NYAL

Important points:

• g before e sounds like a strong breathy sound, similar to a Spanish j
• ni here becomes a ny sound
• the stress is on the last syllable: -nial

So it does not sound like English genial.

No. This is a very important false-friend warning.

In Spanish, genial usually means:

• great
• fantastic
• cool

In English, genial usually means something like:

• friendly
• cheerful
• warm in manner

So Spanish genial is much closer to great than to English genial.

Yes, if the context is already clear.

Spanish often drops information that is obvious from the situation. So if everyone knows you are talking about the concert, Fue genial can mean It was great.

However, when taken alone, fue could in theory come from ser or ir, so context matters. In real conversation, that is usually not a problem.

Genial is common and natural, but it is a bit more informal and expressive than something like bueno or muy bueno.

Compare:

• El concierto fue bueno = The concert was good.
• El concierto fue genial = The concert was great / awesome.

So genial is very useful in everyday speech when you want to sound enthusiastic.