Målgruppen er voksne.

Målgruppen comes from the noun målgruppe, which means target group or target audience.

It is written as one word because Norwegian usually writes compound nouns as a single word:

• mål = target, goal
• gruppe = group

So målgruppe literally means target group, and målgruppen means the target group.

Because Norwegian usually puts the definite article at the end of the noun instead of using a separate word before it.

So:

• målgruppe = target group
• målgruppen = the target group

The ending -en is the definite ending here.

It is grammatically singular.

Even though a target group contains many people, the word målgruppe itself is one group, so Norwegian treats it as a singular noun.

That is very similar to English expressions like the group, the team, or the audience.

Er is the present tense of å være, meaning to be.

A useful thing to know is that Norwegian does not change this verb the way English does:

• jeg er = I am
• du er = you are
• han er = he is
• de er = they are

So er can mean am, is, or are, depending on the subject.

Because voksne means adults or adult people, while voksen usually means adult in the singular.

Compare:

• en voksen = an adult
• voksne = adults

In this sentence, the idea is that the people in the target group are adults, not just one adult, so voksne is used.

It is originally an adjective, but here it is being used like a noun.

This is very common in Norwegian.

So:

• voksen person = adult person
• en voksen = an adult
• voksne = adults

In Målgruppen er voksne, voksne means adults.

Because Norwegian often uses a bare plural after å være when saying what someone is.

Compare:

• De er lærere = They are teachers
• Barna er elever = The children are pupils
• Målgruppen er voksne = The target group is adults

If you said de voksne, that would mean the adults, referring to a specific group of adults.

Yes, in Bokmål that is also possible.

Målgruppe can often appear with two definite singular forms:

• målgruppen
• målgruppa

Both mean the target group.
The version with -a often sounds a bit more informal or reflects a style that uses more feminine noun forms.

A rough pronunciation guide is:

• Målgruppen ≈ MOHL-groo-pen
• er ≈ air
• voksne ≈ VOKS-neh

A few helpful notes:

• å in mål is a long vowel, somewhat like the vowel in British more without a strong r
• u in gruppe is not exactly like English oo, but groo is a useful approximation
• the final -e in voksne is a weak uh sound

Yes, but Målgruppen er voksne is the normal, neutral word order.

It follows standard Norwegian main-clause order:

• subject: Målgruppen
• verb: er
• complement: voksne

You could move things around for emphasis in other contexts, but this version is the most straightforward and natural one for a simple statement.