Razvodna ploča je ovdje.

• razvodna = an adjective describing ploča
• ploča = a noun meaning panel/board
• je = is, the 3rd person singular of biti (to be)
• ovdje = here

So the structure is basically:

[subject] + [is] + [here]

More literally: The distribution panel is here / The electrical panel is here.

Because it agrees with ploča, which is a feminine singular noun.

In Croatian, adjectives change their endings to match the noun in:

• gender
• number
• case

Since ploča is feminine singular nominative, the adjective also takes the feminine singular nominative form: razvodna.

It is in the nominative singular.

That is because razvodna ploča is the subject of the sentence.
The sentence is saying that this thing — the panel — is here.

Also, ovdje is an adverb, not a noun, so there is no case ending on ovdje.

In this sentence, Croatian normally does use je.

Unlike some languages that can omit the present tense of to be, Croatian usually keeps it in ordinary sentences like this:

• On je ovdje. = He is here.
• Ploča je ovdje. = The panel is here.

So Razvodna ploča ovdje would sound incomplete in standard Croatian.

Because je is a clitic — a short, unstressed word that usually goes in the second position in the clause.

Here, the first unit is Razvodna ploča, and then je comes after it:

• Razvodna ploča | je | ovdje.

A useful comparison:

• Razvodna ploča je ovdje.
• Ovdje je razvodna ploča.

In both cases, je comes after the first element of the sentence.

Because Croatian has no articles like English a/an/the.

So razvodna ploča can mean:

• a distribution panel
• the distribution panel

Which one sounds best in English depends on context.
In a real situation, English would often use the here: The electrical panel is here.

Yes. Croatian word order is more flexible than English word order.

These are all possible, with slightly different emphasis:

• Razvodna ploča je ovdje. = neutral
• Ovdje je razvodna ploča. = emphasis on here
• Razvodna ploča ovdje je... = possible only in special styles/contexts, not the normal choice here

So the most natural alternatives are the first two.
Croatian often changes word order to shift emphasis rather than basic meaning.

Yes, you very often can.

Both ovdje and tu can mean here, but:

• ovdje is a bit more explicit and slightly more formal/neutral
• tu is very common in everyday speech

So:

• Razvodna ploča je ovdje.
• Razvodna ploča je tu.

Both are natural. In casual conversation, many speakers would probably use tu.

That is a very reasonable question, because razvod can indeed mean divorce.

But in technical vocabulary, razvodni / razvodna / razvodno often refers to distribution, branching, or routing — especially in electrical contexts.

So razvodna ploča is a fixed technical term meaning something like:

• distribution board
• electrical panel
• switchboard

So here it is definitely not about divorce.

A rough English-style approximation is:

RAHZ-vod-na PLO-cha yeh OV-dyeh

A few helpful sound notes:

• č sounds like ch in church
• j sounds like y in yes
• je is pronounced roughly yeh
• ovdje has a soft dj sound; OV-dyeh is a good approximation for learners

You do not need a perfect accent right away; if you say it close to that, you will usually be understood.

It is mainly a technical/practical term.

Depending on context, English translations might be:

• distribution board
• electrical panel
• breaker panel
• switchboard

So even though the sentence grammar is simple, the noun phrase itself is somewhat specialized vocabulary.

Yes. A few natural alternatives are:

• Ovdje je razvodna ploča.
  Same meaning, but with more focus on here.

• Razvodna ploča je tu.
  More conversational.

• Razvodna ploča nalazi se ovdje.
  More formal, more like The panel is located here.

So the original sentence is completely correct and natural, but it is not the only possible way to express the idea.