Spillbrettet ligger på bordet.

Because Norwegian usually writes compound nouns as one word.

So where English has game board, Norwegian has spillbrett.
Then the definite ending is added to the whole compound:

• et spillbrett = a game board
• spillbrettet = the game board

This is very normal in Norwegian.

It is made from:

• spill = game
• brett = board / tray / flat surface

Together, spillbrett means game board.
In the sentence, it appears as spillbrettet, which is the definite singular form: the game board.

A useful thing to notice is that in Norwegian compounds, the grammatical ending usually goes on the last part:

• spill + brett → spillbrett
• spillbrett + -et → spillbrettet

Because both nouns are neuter nouns in the definite singular.

• et spillbrett → spillbrettet
• et bord → bordet

So -et here means something like the for neuter singular nouns.

This is one of the main patterns in Norwegian:

• en noun often becomes definite with -en
• et noun often becomes definite with -et

Norwegian usually does not use a separate word like English the in simple noun phrases like this. Instead, the definite article is attached to the end of the noun.

So:

• spillbrettet = the game board
• bordet = the table

This is why there is no separate word for the in the sentence.

Norwegian often prefers a position verb when talking about where something is.

Here, ligger comes from å ligge, which means to lie. It is used for something that is resting in a lying or flat position.

A board on a table is naturally thought of as lying on the table, so ligger sounds very natural.

Compare:

• Spillbrettet ligger på bordet. = the board is lying/on the table
• Spillbrettet er på bordet. = the board is on the table

The second one is grammatical, but ligger is more specific and more idiomatic for this kind of object.

Ligger is the present tense of å ligge.

Some useful forms are:

• å ligge = to lie
• ligger = lies / is lying
• lå = lay / was lying
• har ligget = has/have lain / been lying

So in this sentence, ligger means is lying or simply is in a location sense.

På is the normal preposition for on when something is on top of a surface.

So:

• på bordet = on the table

That makes perfect sense here because the game board is resting on the table’s surface.

Like many prepositions, på can have other meanings in other contexts, but in this sentence it is the straightforward on.

This is the normal Norwegian main-clause order:

• subject: Spillbrettet
• verb: ligger
• prepositional phrase: på bordet

So it follows a basic pattern similar to English:

• The game board
  • is lying
    • on the table

It also fits the important Norwegian V2 rule: in main clauses, the finite verb usually comes in the second position.

For example, you could also say:

• På bordet ligger spillbrettet.

Here på bordet comes first, but the verb ligger still stays in second position.