Bildeteksten beskriver lysbildet.

• bildeteksten = the caption or the image caption
• lysbildet = the slide

A few details:

• bildetekst is a compound noun:
  • bilde = image, picture
  • tekst = text
  • together: caption / image text
• lysbilde literally means something like light-picture, but in modern use it commonly means slide, such as a presentation slide.

So the sentence is talking about a caption describing a slide.

Those endings mark the definite form in Norwegian.

• bildetekst → bildeteksten = the caption
• lysbilde → lysbildet = the slide

Unlike English, Norwegian often adds the to the end of the noun instead of putting a separate word in front.

Very roughly:

• masculine nouns often take -en
• neuter nouns often take -et

Here:

• bildetekst is masculine → bildeteksten
• lysbilde is neuter → lysbildet

You usually learn the gender along with the noun.

The dictionary forms are:

• en bildetekst
• et lysbilde

That tells you the gender:

• en = common gender in Bokmål, often called masculine in teaching materials
• et = neuter

Then the definite forms become:

• en bildetekst → bildeteksten
• et lysbilde → lysbildet

For a learner, the safest habit is to memorize nouns with their article:

• en bildetekst
• et lysbilde

beskriver is the present tense of the verb å beskrive, which means to describe.

So:

• å beskrive = to describe
• beskriver = describes / is describing

In this sentence:

• Bildeteksten beskriver lysbildet = The caption describes the slide

Norwegian present tense is often simpler than English because the verb does not change depending on the subject:

• jeg beskriver = I describe
• du beskriver = you describe
• han/hun beskriver = he/she describes

It stays beskriver for all persons.

Because Norwegian usually puts definiteness on the noun itself.

Compare:

• English: the caption

• Norwegian: bildeteksten

• English: the slide
• Norwegian: lysbildet

So instead of a separate article like the, Norwegian commonly uses a suffix:

• -en
• -et
• sometimes -a or -ene, depending on the noun

This is one of the biggest structural differences from English.

This sentence uses the basic Norwegian word order:

subject + verb + object

• Bildeteksten = subject
• beskriver = verb
• lysbildet = object

So it is a very straightforward sentence.

Norwegian main clauses normally follow the V2 rule, meaning the verb is in the second position. In this sentence, that happens naturally:

• first element: Bildeteksten
• second element: beskriver

Then the object comes after the verb.

Yes, depending on context.

Norwegian present tense often covers both:

• simple present: describes
• present progressive: is describing

So beskriver can correspond to either English form.

Which one sounds best in English depends on the situation:

• general statement: The caption describes the slide
• ongoing action or immediate context: The caption is describing the slide

But grammatically, Norwegian just uses beskriver.

Because Norwegian usually writes compound nouns as one word.

So:

• bilde
  • tekst → bildetekst
• lys
  • bilde → lysbilde

This is very common in Norwegian and often different from English, which may use:

• one word
• two words
• or a hyphen

A native English speaker often wants to separate these, but in Norwegian, compounds are very often written together.

The indefinite forms are:

• en bildetekst = a caption
• et lysbilde = a slide

So the sentence in an indefinite version could be:

En bildetekst beskriver et lysbilde.

That means:

• A caption describes a slide

This is useful because it helps you see the base noun forms:

• bildetekst
• lysbilde

Yes. Lysbilde can mean a slide, including a presentation slide.

Depending on context, Norwegian speakers may also use:

• slide
• PowerPoint-slide
• or other context-specific wording

But lysbilde is a normal Norwegian word and is perfectly understandable.

So in a learning sentence like this, lysbildet is naturally read as the slide.

No. lysbilden is not the correct form.

The correct definite singular of et lysbilde is:

• lysbildet

That is because lysbilde is a neuter noun:

• et lysbilde
• lysbildet

If it were plural definite, it would be:

• lysbildene = the slides

So:

• singular indefinite: et lysbilde
• singular definite: lysbildet
• plural indefinite: lysbilder
• plural definite: lysbildene

You would normally put ikke after the verb:

Bildeteksten beskriver ikke lysbildet.

That means:

• The caption does not describe the slide

This is a useful pattern to remember:

• subject + verb + ikke
  • object

For example:

• Han forstår ikke teksten.
• Jeg liker ikke bildet.

So in your sentence:

• Bildeteksten = subject
• beskriver = verb
• ikke = not
• lysbildet = object

A rough guide is:

BIL-de-tek-sten be-SKRI-ver LYS-bil-det

A few helpful notes:

• bildeteksten has the stress early: BIL-
• beskriver has stress on SKRI
• lysbildet usually has stress on LYS

Also:

• Norwegian y in lys does not sound like English y
• it is a rounded vowel that many English speakers need to practice separately

You do not need perfect pronunciation at first, but it helps to notice where the stress falls.