Dækningen er god.

Because Danish usually puts the definite article on the end of the noun.

• dækning = coverage
• dækningen = the coverage

So -en here is the definite ending for a singular en-word.
This is one of the big differences from English, where you would normally put the before the noun instead.

It is an en-word:

• en dækning
• dækningen

That matters because it affects both the definite form and adjective agreement.

Because god agrees with a singular en-word when it is used after er.

Here is the basic pattern:

• en-word, singular: god
• et-word, singular: godt
• plural: gode

Examples:

• Dækningen er god.
• Signalet er godt.
• Forholdene er gode.

A useful detail: even though dækningen is definite, the adjective stays god here because it is a predicative adjective, meaning it comes after er. After er, definiteness does not change it to gode.

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

Unlike English, Danish uses the same present-tense form for all persons:

• jeg er = I am
• du er = you are
• han/hun er = he/she is
• vi er = we are

So in Dækningen er god, er simply means is.

Because Danish often prefers the definite form when the coverage is understood from the situation.

So if you are talking about the phone signal, network coverage, or some other specific coverage in a place, Dækningen er god is very natural: The coverage is good.

English often uses a bare noun more freely:

• Coverage is good here.

Danish often sounds more natural with the definite noun in that kind of context:

• Dækningen er god her.

A rough learner-friendly approximation is DEK-ning-en.

A few pronunciation notes:

• æ is roughly like the vowel in cat, though not exactly the same
• the -en ending is usually light and unstressed
• the whole word is said smoothly, not as three strongly separate parts

If you say something close to DEK-ning-en, Danish speakers will usually understand you.

Yes. That is a different structure.

• god dækning = good coverage
• dækningen er god = the coverage is good

So:

• Vi har god dækning her. = We have good coverage here.
• Dækningen er god her. = The coverage is good here.

The first is a noun phrase.
The second is a full sentence.

Yes, very natural.

It means There is good coverage.

This is often one of the most common ways to say it in everyday Danish:

• Der er god dækning her. = There is good coverage here.

Compare:

• Der er god dækning. = There is good coverage.
• Dækningen er god. = The coverage is good.

Both are correct, but the focus is a little different.
Der er god dækning introduces the situation.
Dækningen er god comments on the coverage itself.

Yes. Dækning can refer to different kinds of coverage depending on context, for example:

• mobile/network coverage
• insurance coverage
• media coverage

So the grammar of the sentence stays the same, but the exact meaning depends on the situation. Many learners first meet it in the sense of phone or signal coverage.

You move the verb before the subject:

• Er dækningen god? = Is the coverage good?

That is standard Danish word order for yes/no questions.

So you can compare:

• Dækningen er god. = statement
• Er dækningen god? = question

It is the normal word order for a simple Danish main clause:

• subject
  • verb
    • complement

So here:

• Dækningen = subject
• er = verb
• god = complement/adjective

Danish also follows the verb-second rule in main clauses. That means if you put something else first, the verb still stays in second position:

• Her er dækningen god. = Here, the coverage is good.
• I dette område er dækningen god. = In this area, the coverage is good.