Daarin legt ze uit waarom elk klein detail ertoe kan doen.

Daarin means in that or in it.

It is made from:

• daar = there / that
• in = in

Together, daarin refers back to something previously mentioned, such as a book, article, video, explanation, report, or message.

So in context, it means something like in that piece / in it / there, she explains...

Because Dutch main clauses usually follow the verb-second rule.

That means the finite verb comes in the second slot of the sentence. Here, Daarin is placed first, so the verb legt must come next:

• Daarin = first position
• legt = second position
• ze = subject, after the verb

So:

• Ze legt daarin uit ... = neutral starting with she
• Daarin legt ze uit ... = starting with in that / there

Both are possible, but they emphasize different parts of the sentence.

Because the verb is uitleggen, which is a separable verb.

Its two parts are:

• uit
• leggen

In a main clause, the finite part moves to the usual verb position, and the prefix goes to the end:

• ze legt uit = she explains

Compare:

• Ik leg het uit.
• Ze legt uit waarom ...

But in some other forms, the parts stay together:

• Ze wil het uitleggen.
• Omdat ze het uitlegt...

So you should learn uitleggen as one verb, even though it splits in many sentences.

Because waarom means why, and this sentence contains an indirect question:

• ze legt uit waarom ...
• she explains why ...

Omdat means because, and it introduces the reason itself, not the question about the reason.

Compare:

• Ze legt uit waarom het belangrijk is.
  = She explains why it is important.

• Het is belangrijk omdat...
  = It is important because...

So after uitleggen in this sentence, waarom is the right choice.

Ertoe doen is a fixed expression meaning:

• to matter
• to make a difference
• to be important

A very common sentence is:

• Het doet ertoe. = It matters.

So here:

• elk klein detail ertoe kan doen
• every small detail can matter

It is best to learn ertoe doen as a whole expression, because the literal parts do not map neatly onto natural English.

Because Dutch often splits up expressions when there is a verb cluster at the end.

The full expression is ertoe doen, but when another verb such as kan is present, you often get:

• ... ertoe kan doen

So although ertoe doen belongs together in meaning, Dutch word order allows kan to come between the non-verbal part and the infinitive.

A good way to understand it is:

• learn the expression as ertoe doen
• accept that in real sentences it may look split up

Because kan adds the idea of possibility or potential.

• doet ertoe = matters
• kan ertoe doen = can matter / may matter

So this sentence does not say that every small detail definitely matters in every case. It says that every small detail can matter.

That makes the statement slightly softer and more general.

Because elk means each or every, and in Dutch it is followed by a singular noun.

So:

• elk detail = every detail
• elk klein detail = every small detail

This works like English every detail, not every details.

If you wanted a plural idea, you would use something like:

• alle kleine details = all the small details

Because detail is a het-word:

• het detail

With a singular neuter noun after an indefinite-type determiner such as elk, the adjective usually does not take -e.

So:

• elk klein detail
• elk mooi huis

But with a definite form, you do get -e:

• het kleine detail
• het mooie huis

This is one of the standard adjective-ending patterns in Dutch.

Ze can mean either:

• she
• they

Only the context tells you which one is meant.

In this sentence, the meaning shown to the learner makes it clear that it means she. But grammatically, ze by itself could also be plural in another context.

Often yes, but there is a small difference in feel.

• daarin is a bit more explicit and clearly points back to something
• erin is more reduced and often sounds more conversational

So both can be possible in many contexts, but daarin may sound slightly clearer or a little more formal.

For example:

• Daarin legt ze uit ...
• Erin legt ze uit ...

The first one is often the safer choice for learners when referring back to something already mentioned.