Varene er klare.

Because Norwegian usually puts the definite article at the end of the noun.

So:

• vare = item / product
• varene = the items / the goods

The ending -ne marks definite plural.
So varene already includes the idea of the.

The base form is en vare.

Here are the basic forms:

• en vare = an item / a product
• varen = the item / the product
• varer = items / products
• varene = the items / the products

So in Varene er klare, varene is plural definite.

Because the adjective has to agree with the noun.

Here, varene is plural, so the adjective takes the plural form klare.

Compare:

• Varen er klar. = The item is ready.
• Varene er klare. = The items are ready.

A useful pattern is:

• singular common gender: klar
• singular neuter: klart
• plural: klare

Here it is an adjective.

In Varene er klare, the structure is:

• Varene = subject
• er = verb
• klare = adjective describing the subject

So klare means ready here.

This is different from the verb å klare, which means to manage / to be able to cope with.

For example:

• Jeg klarer det. = I can manage it.

But in your sentence, klare is not a verb.

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

Unlike English, Norwegian does not change this verb for person or number in the present tense:

• jeg er = I am
• du er = you are
• han er = he is
• vi er = we are
• varene er = the goods are

So er works for all subjects in the present tense.

This is the normal word order for a simple Norwegian statement:

subject + verb + complement

So:

• Varene = subject
• er = verb
• klare = complement

This is very similar to English: The goods are ready.

If you turn it into a yes/no question, the verb comes first:

• Er varene klare? = Are the goods ready?

You would say:

Er varene klare?

Norwegian usually forms yes/no questions by putting the verb before the subject.

So:

• statement: Varene er klare.
• question: Er varene klare?

A rough pronunciation guide is:

VAA-re-ne er KLAA-re

A few helpful points:

• v is pronounced like English v
• a is usually a broad ah sound
• r is often tapped or lightly rolled, depending on dialect
• the final e in varene and klare is usually a weak vowel, like uh

The exact pronunciation depends on dialect, but in standard East Norwegian it will sound roughly like:

VAH-reh-neh ær KLAH-reh

It can mean several related things, depending on context:

• goods
• items
• products
• merchandise

So Varene er klare could be used in different situations, for example:

• in a shop
• in a warehouse
• for an order
• for groceries or purchased items

The exact English translation depends on context, but the Norwegian sentence itself is perfectly natural.

Yes, but it changes the meaning.

• Varene er klare. = The goods are ready.
  This refers to specific goods.

• Varer er klare. = Goods are ready.
  This is more general and is less likely in many everyday situations.

In most real contexts, if you mean a specific order or specific products, varene is the more natural choice.