Фигурка, которую сделал мой сын, стоит на полке.

Because которую is in the accusative case.

In the relative clause которую сделал мой сын, the word которую refers back to фигурка, but inside that clause it functions as the direct object of сделал:

• мой сын сделал фигурку = my son made the figurine

Since фигурка is feminine singular, the relative pronoun must also be feminine singular, but in the accusative:

• nominative: которая
• accusative: которую

So:

• Фигурка... = the figurine
• которую сделал мой сын = that my son made

Сделал is the perfective past tense of сделать, while делал is the imperfective past tense of делать.

Here, the sentence talks about a completed result: the son finished making the figurine. That is why Russian normally uses сделал.

• сделал = made, has made, finished making
• делал = was making / used to make / made in a process-focused way

So:

• которую сделал мой сын = which my son made / which my son has made
• которую делал мой сын would suggest more of an ongoing process, and sounds less natural here if the figurine is already a finished object sitting on the shelf

Because мой сын is the subject of the verb сделал.

Inside the relative clause:

• мой сын сделал фигурку

Here:

• мой сын = subject, so nominative
• фигурку = direct object, so accusative

Even though the whole sentence starts with Фигурка, the clause которую сделал мой сын has its own internal grammar, and inside that clause мой сын is the one performing the action.

Because this is a relative clause inserted into the main sentence.

The full structure is:

• Фигурка ... стоит на полке.
• inserted description: которую сделал мой сын

Russian normally sets off this kind of descriptive subordinate clause with commas.

So the sentence is divided like this:

• Фигурка, которую сделал мой сын, стоит на полке.

This is very similar to English:

• The figurine, which my son made, is standing on the shelf.

Even though English punctuation rules are not always identical, in Russian the commas are required here.

Russian often uses verbs like:

• стоять = to stand
• лежать = to lie
• сидеть = to sit

when describing where something is located.

So:

• Фигурка стоит на полке literally means The figurine is standing on the shelf

In natural English, we often just say is on the shelf, but Russian prefers a more specific position verb here.

Also, Russian usually does not use a present-tense equivalent of is in simple location sentences.

So Russian says:

• Фигурка стоит на полке not
• Фигурка есть на полке in normal speech

Because на полке expresses location, not movement.

With на, Russian uses different cases depending on the meaning:

• на + accusative = motion onto something
• на + prepositional = location on something

Compare:

• поставить фигурку на полку = to put the figurine onto the shelf
• фигурка стоит на полке = the figurine is on the shelf

Here the figurine is already there, so Russian uses the prepositional case:

• полка → на полке

Because the relative clause is describing фигурка, and Russian places it directly after the noun it modifies.

Structure:

• Фигурка = the noun
• которую сделал мой сын = description of that noun
• стоит на полке = main statement

So the sentence means:

• The figurine that my son made is on the shelf

Russian often puts the descriptive clause immediately after the noun, then continues with the main verb.

Yes, Russian word order is fairly flexible, though not every version sounds equally natural.

For example, you could also say:

• Фигурка, которую мой сын сделал, стоит на полке.

This is also correct. It just changes the internal word order of the relative clause slightly.

You could even say:

• На полке стоит фигурка, которую сделал мой сын.

This version emphasizes the location first: On the shelf stands the figurine that my son made.

So the original sentence is natural, but not the only possible order.

Because past-tense verbs in Russian agree with the subject in gender and number.

The subject of сделал is сын, which is masculine singular. So the verb is:

• masculine singular: сделал

Compare:

• мой сын сделал = my son made
• моя дочь сделала = my daughter made
• мои дети сделали = my children made

So the form сделал tells you that the person who made it is masculine singular.

Not exactly. Фигурка usually means a small figure, figurine, small sculpture, or sometimes a little shaped object.

It is the diminutive form of фигура, so it often has the sense of something small or shaped like a figure.

In this sentence, the most natural English translation is usually:

• figurine
• sometimes little figure

So a learner should not automatically translate it as figure in every context.

Because Russian has no articles like a, an, or the.

So Фигурка can mean:

• a figurine
• the figurine

The exact meaning depends on context.

In this sentence, because the figurine is specifically identified by the clause которую сделал мой сын, English would normally use the:

• The figurine that my son made is on the shelf.

Russian expresses that specificity through context and structure, not through an article.

Yes, but it would usually sound more formal or bookish.

A participial version might be:

• Фигурка, сделанная моим сыном, стоит на полке.

This means essentially the same thing:

• The figurine made by my son is on the shelf.

Compare the two:

• которую сделал мой сын = more straightforward, common in everyday speech
• сделанная моим сыном = more compact, but often more formal or written

For most learners, the relative clause version is easier and more useful at first.

A simpler version would be:

• Мой сын сделал фигурку. Фигурка стоит на полке.

This means:

• My son made a figurine. The figurine is on the shelf.

The original sentence combines those two ideas into one:

• Фигурка, которую сделал мой сын, стоит на полке.

This is a very common Russian pattern:

• noun + который clause + main verb

It is worth learning because it is one of the main ways Russian says the X that...