I dag lærer vi udtrykket “have brug for”, når vi taler om noget, vi behøver.

Because Danish is a V2 language in main clauses. That means the finite verb normally comes in the second position.

Here, I dag is placed first:

• I dag = first position
• lærer = second position
• vi = subject after the verb

So:

• I dag lærer vi ... = Today we are learning ...

A more neutral order would be:

• Vi lærer udtrykket ... i dag.

Both are possible, but the version with I dag first is very natural.

Udtryk means expression.

Danish often adds the definite article to the end of the noun:

• et udtryk = an expression
• udtrykket = the expression

So udtrykket is the definite singular form. It is used here because the speaker is introducing one specific expression: have brug for.

Because when Danish names a verb or a verb phrase, it usually uses the infinitive/base form.

So the expression is listed as:

• have brug for

But in real sentences, it gets conjugated:

• jeg har brug for ... = I need ...
• vi har brug for ... = we need ...
• hun havde brug for ... = she needed ...

So have brug for is the dictionary-style form, while har brug for is an actual present-tense form.

It is a fixed expression meaning to need.

You should learn it as a whole phrase, not translate each word separately.

Examples:

• Jeg har brug for hjælp. = I need help.
• Vi har brug for mere tid. = We need more time.
• Hun har brug for at sove. = She needs to sleep.

So even though the individual words look like have + use + for, the natural meaning is simply need.

They are often very close in meaning.

• have brug for = to need
• behøve = to need

In your sentence, behøver is the present tense of behøve.

Examples:

• Jeg har brug for hjælp.
• Jeg behøver hjælp.

Both can mean I need help.

A useful difference to notice:

• have brug for is very common in everyday Danish
• behøve is also common, and it is especially common in negative sentences

For example:

• Du behøver ikke komme. = You do not need to come.

So the sentence is explaining one way to express need, while using another common verb for comparison.

Here når means when or whenever.

It introduces a subordinate clause:

• når vi taler om noget, vi behøver

So the full idea is:

• Today we are learning the expression have brug for, when we talk about something we need.

In teaching language like this, når often has a general meaning: when/whenever we are talking about this kind of situation.

Because når introduces a subordinate clause, and subordinate clauses do not follow the same V2 pattern as main clauses.

So after når, the normal order is:

• subject + verb
• vi taler

Compare:

• Main clause: I dag lærer vi ...
• Subordinate clause: når vi taler ...

That is a very important Danish word-order pattern to learn.

Because tale om is the normal Danish expression for talk about.

So:

• tale om noget = to talk about something

The preposition om belongs with tale here. It is not part of have brug for.

So this part breaks down as:

• når vi taler om noget = when we talk about something

This means:

• something (that) we need

Danish often leaves out som in this kind of relative clause, just as English often leaves out that.

So these are both possible:

• noget, vi behøver
• noget, som vi behøver

The version without som is very natural.

So:

• noget, vi behøver = something we need

The commas mark subordinate clauses.

In this sentence, they appear before:

• når vi taler om noget, vi behøver
• vi behøver

Danish comma usage can vary depending on which accepted comma style is being used. In a style with start comma, these commas are normal.

So you may also see similar sentences written with fewer commas in other contexts, but the version shown here is perfectly standard.

I dag means today.

It is written as two words in modern Danish:

• i dag

Yes, it can move.

For example:

• I dag lærer vi udtrykket ...
• Vi lærer udtrykket ... i dag.

Both are grammatical. Putting I dag first gives it extra focus and causes the verb to come before the subject, which is why you get lærer vi.