В декабре на площади стоит высокая ёлка, и вечером там особенно красиво.

Because Russian uses в + prepositional case for most months when meaning in a month.

• декабрь = December
• в декабре = in December

This is the prepositional singular form of декабрь.

Compare:

• в январе = in January
• в мае = in May
• в сентябре = in September

So В декабре simply means In December.

Russian usually uses на with open public spaces like squares, islands, bridges, stadiums, and similar locations.

So:

• на площади = in the square / on the square

Even though English says in the square, Russian normally says на площади.

This is also prepositional case after на:

• площадь → на площади

A few similar examples:

• на улице = on the street / in the street
• на стадионе = at the stadium
• на мосту = on the bridge

Russian often prefers a position verb where English would simply use is.

Here:

• стоять = to stand
• стоит = stands / is standing

For upright things, Russian commonly uses стоять:

• a tree
• a bottle
• a building
• a monument

So на площади стоит высокая ёлка literally means A tall tree stands in the square, but in natural English you might translate it as There is a tall Christmas tree in the square.

This is very normal Russian usage.

Both words are in the nominative singular feminine.

• ёлка is a feminine noun
• высокая is the adjective and must agree with it

So:

• высокий = tall, high
• feminine nominative singular: высокая
• ёлка = tree

Together:

• высокая ёлка = a tall tree

The noun is nominative because it is the grammatical subject of стоит.

It can mean both, depending on context.

• ель is the basic dictionary word for fir/spruce
• ёлка can mean fir tree/spruce tree, but very often it means a decorated New Year or Christmas tree

In this sentence, because of December, the square, and especially beautiful in the evening, most learners would understand ёлка here as a public holiday tree, probably decorated with lights.

So in context, ёлка is very likely the big New Year/Christmas tree in the square.

Because и is joining two separate clauses:

1. В декабре на площади стоит высокая ёлка
2. вечером там особенно красиво

The second part is basically an impersonal clause: it is especially beautiful there in the evening.

In Russian, when и connects two independent clauses, a comma is usually needed.

So the comma is correct here.

Вечером is the instrumental case of вечер, and it is often used adverbially to mean:

• in the evening
• during the evening
• at nightfall, depending on context

This is a very common pattern in Russian:

• утром = in the morning
• днём = in the daytime / during the day
• вечером = in the evening
• ночью = at night

So вечером там особенно красиво means It is especially beautiful there in the evening.

You should learn these as common time expressions.

Там means there.

Here it refers back to на площади.

So instead of repeating на площади, Russian uses там:

• вечером там особенно красиво = it is especially beautiful there in the evening

This makes the sentence sound more natural and less repetitive.

Because красиво here is not an adjective describing a noun. It is an adverb/predicative word meaning:

• beautifully
• beautiful there
• it is beautiful

In this sentence, Russian uses an impersonal construction:

• там особенно красиво = it is especially beautiful there

There is no noun that красиво is agreeing with, so it does not take endings like красивая, красивый, or красивое.

Compare:

• красивая ёлка = a beautiful tree
  
  • adjective agreeing with ёлка
• там красиво = it is beautiful there
  
  • predicative/adverbial use

Особенно means especially.

It modifies красиво:

• особенно красиво = especially beautiful

So the sentence means that in the evening, the square is not just beautiful, but especially beautiful.

Yes, Russian word order is flexible.

This sentence starts with time and place:

• В декабре = in December
• на площади = in the square

Then it introduces what is there:

• стоит высокая ёлка

This is very natural because Russian often goes from setting to main information.

You could rearrange it, for example:

• Высокая ёлка стоит на площади в декабре...

But that would sound different in emphasis. The original feels smoother and more descriptive.

A rough information flow is:

1. When? — in December
2. Where? — in the square
3. What is there? — a tall tree
4. And what is it like later? — especially beautiful there in the evening

Yes, стоит is present tense, third person singular, from стоять.

But in Russian, the present tense is often used for a general current situation, not only for something happening at this exact second.

So here it means something like:

• In December, a tall tree stands in the square
• or more naturally, In December there is a tall tree in the square

It describes a seasonal scene, not necessarily a moment-by-moment action.

Yes. In many Russian texts, ё is often written as е, so you may see елка.

But the pronunciation is still ё:

• ёлка = pronounced roughly YOL-ka

For learners, writing ё is very helpful because it shows the correct pronunciation and stress more clearly.

So:

• ёлка = clearer and better for study
• елка = common in ordinary print

Both represent the same word.

Yes.

English often says:

• There is a tall tree in the square

Russian usually does not need a separate word like English there is. It simply says:

• На площади стоит высокая ёлка

Literally:

• In the square stands a tall tree

This is one of the most common differences between English and Russian sentence structure. Russian often just places the thing in a location and uses a normal verb such as:

• стоять = stand
• лежать = lie
• висеть = hang
• быть is often omitted in the present tense in these kinds of sentences

So yes, this is a very typical Russian pattern.