Банный веник нужно подготовить.

Not quite in the ordinary English sense of broom.

In everyday Russian, веник can mean a broom made of twigs, but in the context of a баня (Russian bathhouse/steam bath), банный веник means a bundle of leafy branches used in the steam room for gently hitting or massaging the body.

So in this sentence, банный веник is best understood as a bath whisk or banya whisk, not a floor-cleaning broom.

Банный is an adjective meaning related to the bathhouse / bath / banya.

It comes from баня, which usually means a bathhouse or specifically a Russian steam bath.

So:

• баня = bathhouse, banya
• банный = bathhouse-related, bath-related

In банный веник, it tells you what kind of веник it is: the kind used in a bathhouse.

It is in the accusative singular, because it is the direct object of подготовить.

You are preparing what?
→ банный веник

However, for an inanimate masculine noun, the accusative singular looks exactly like the nominative singular:

• nominative: банный веник
• accusative: банный веник

So the form does not change, even though the case function does.

Нужно is an impersonal predicate meaning it is necessary, it is needed, or one must.

In sentences like this, Russian often does not use a personal subject like I, you, or we. Instead, it uses an impersonal structure:

• нужно + infinitive

So:

• нужно подготовить = it is necessary to prepare / one needs to prepare

This is a very common Russian pattern.

Because after нужно, Russian normally uses an infinitive.

Pattern:

• нужно сделать
• нужно идти
• нужно читать
• нужно подготовить

So нужно подготовить literally means it is necessary to prepare.

English often uses:

• You need to prepare...
• It is necessary to prepare...
• The ... needs to be prepared

Russian does not need to name the person doing the action.

This is mainly about aspect.

Подготовить is perfective, so it focuses on completing the preparation: to prepare, to get ready fully.

That fits well here, because the sentence is about achieving a result:

• the bath whisk should be made ready

Compare:

• подготовить = to prepare completely, to get ready
• подготавливать = to be preparing / to prepare repeatedly or as a process
• готовить = to prepare in a broader sense; often to cook in many contexts

So нужно подготовить means something like it needs to be properly prepared.

Yes. That is a very natural translation.

Depending on context, English could render it as:

• The bath whisk needs to be prepared.
• You need to prepare the bath whisk.
• It is necessary to prepare the bath whisk.

All of these can match Банный веник нужно подготовить.

Russian leaves the doer unspecified, so English can choose the most natural wording for the situation.

Yes, Нужно подготовить банный веник is also correct.

Russian word order is more flexible than English, and moving words changes emphasis more than basic grammar.

• Банный веник нужно подготовить.
  This puts extra attention on банный веник. It can sound like As for the bath whisk, it needs to be prepared.

• Нужно подготовить банный веник.
  This is often a more neutral order: It is necessary to prepare the bath whisk.

So the original sentence is correct; it just foregrounds the object a bit.

Not explicitly.

Russian often uses impersonal sentences where English would naturally supply a subject. In context, the understood meaning might be:

• you need to prepare it
• we need to prepare it
• someone needs to prepare it

But the Russian sentence itself does not say who must do it. It only says that the action is necessary.

Because Russian has no articles.

So банный веник can mean:

• a bath whisk
• the bath whisk

The exact meaning depends on context.

If the object is already known in the conversation, English may use the.
If it is being mentioned more generally, English may use a.

Russian leaves that to context rather than using articles.

A natural pronunciation is:

ба́нный ве́ник ну́жно подгото́вить

Stress:

• ба́нный
• ве́ник
• ну́жно
• подгото́вить

A rough pronunciation guide:

• BAHN-nyy VYE-nik NOOZH-na puh-duh-TO-vitʹ

The final -ть in подготовить is soft.

Yes, веник is a masculine noun.

You can tell from:

• its dictionary form ending
• the adjective agreement: банный is masculine singular

If it were feminine or neuter, the adjective would look different:

• masculine: банный
• feminine: банная
• neuter: банное

So банный веник shows masculine agreement.

Yes. Надо подготовить банный веник is also correct and very common.

Both нужно and надо can mean need to / must / it is necessary to.

Very roughly:

• надо often sounds a bit more conversational
• нужно can sound slightly more neutral or formal

But in many everyday situations, they are interchangeable.

Yes, very possibly.

In the context of a банный веник, подготовить usually means getting it ready for use in the steam bath. That may involve things like:

• soaking it in water
• softening the branches and leaves
• warming it properly

So this is not just a vague prepare; in context it often refers to the specific traditional process of making the whisk usable in the banya.