Skibindingen holder skiskoen på plass.

Because Norwegian usually writes compound nouns as one word.

• skibindingen = ski
  • bindingen
• skiskoen = ski
  • skoen

The last part is the main noun, so:

• a skibinding is a kind of binding
• a skisko is a kind of shoe/boot

This is very normal in Norwegian. English sometimes writes similar things as two words, but Norwegian much more often joins them.

The ending -en marks the definite singular form, like the in English.

So:

• en skibinding = a ski binding
• skibindingen = the ski binding

and

• en skisko = a ski boot
• skiskoen = the ski boot

So the sentence uses definite nouns because it is talking about the binding and the boot, not just any binding or boot.

Because in Norwegian, definiteness is usually built into the noun itself.

English uses a separate word:

• the ski binding
• the ski boot

Norwegian usually adds an ending instead:

• skibindingen
• skiskoen

So the meaning of the is already contained in -en.

Holder is the present tense of holde.

• å holde = to hold / to keep
• holder = holds / is holding / keeps

A useful point for learners: in Norwegian, the present tense form does not change for different subjects.

• jeg holder
• du holder
• han holder
• de holder

So holder is the normal present-tense form here.

På plass literally means something like in place or in the correct position.

In this sentence, it means the binding keeps the boot:

• secure
• properly positioned
• where it should be

So holde noe på plass is a very common expression meaning to hold something in place.

This is the normal word order for a simple Norwegian main clause:

Subject + Verb + Object + Adverbial

So here:

• Skibindingen = subject
• holder = verb
• skiskoen = object
• på plass = adverbial phrase

That is the most natural order in a neutral statement like this.

Not naturally in this sentence.

The usual order is:

holder skiskoen på plass

because på plass belongs closely with the idea of what happens to skiskoen. Putting på plass before the object sounds awkward here.

So the most idiomatic version is:

Skibindingen holder skiskoen på plass.

Because the sentence is describing the relationship between one binding and one boot.

In real life, skis come in pairs, but each binding holds one boot. So singular makes perfect sense.

If you wanted to talk about both bindings and both boots, you could say:

Skibindingene holder skiskoene på plass.

That would mean the ski bindings hold the ski boots in place.

Sometimes, yes.

Many nouns ending in -ing can be treated as feminine in Norwegian, especially in some dialects and in less conservative Bokmål usage. That means you may see:

• skibindingen
• skibindinga

Both can be understandable, but skibindingen is a very safe standard Bokmål form.

By contrast, skiskoen normally stays -en, because sko is not usually treated as a feminine noun.

Yes. In Norwegian compounds, the last part is the main category, and the first part modifies it.

So:

• binding = the basic noun
• skibinding = a binding for skis

and

• sko = the basic noun
• skisko = a shoe/boot for skiing

This is a very useful pattern to learn, because Norwegian uses compound nouns constantly.