La leçon dure trente minutes.

In French, you usually need an article before a singular noun when you mean the lesson or a lesson.

• la leçon = the lesson
• une leçon = a lesson

Using leçon by itself would usually sound incomplete in a normal sentence.

Because leçon is a feminine noun in French.

French nouns have grammatical gender, so:

• le is used with masculine singular nouns
• la is used with feminine singular nouns

Since leçon is feminine, you say la leçon.

Dure is the verb durer in the present tense.
Durer means to last.

So:

• La leçon dure trente minutes = The lesson lasts thirty minutes

Here, dure means lasts.

Because durer is the infinitive form, meaning to last.

In a normal sentence with a subject, you usually need a conjugated verb:

• durer = to last
• la leçon dure = the lesson lasts

So dure is the third-person singular present form, matching la leçon.

Because la leçon is a third-person singular subject: the lesson.

In the present tense, durer is conjugated like this:

• je dure
• tu dures
• il/elle/on dure
• nous durons
• vous durez
• ils/elles durent

Since la leçon is like elle, the correct form is dure.

In French, after durer, you normally give the length of time directly, without adding a word for for.

So French says:

• La leçon dure trente minutes

Literally, that is closer to:

• The lesson lasts thirty minutes

English often allows lasts thirty minutes or lasts for thirty minutes, but French usually just uses the duration directly after durer.

Because trente means thirty, so the noun must be plural.

• une minute = one minute
• trente minutes = thirty minutes

French makes the noun plural here, just like English does.

That is the normal word order in French, just as in English:

• trente minutes = thirty minutes

The number comes first, then the noun.

Yes. Trente is the basic French word for thirty, and it is written as one word.

Examples:

• trente minutes = thirty minutes
• trente élèves = thirty students
• trente euros = thirty euros

A simple pronunciation guide is:

la luh-son dur tront mee-newt

A few helpful details:

• la sounds like lah
• leçon sounds roughly like luh-son
  
  • the ç makes an s sound
  • the final -on is a nasal sound, not a full English on
• dure sounds roughly like dur
  
  • the u is a French sound that does not exist exactly in English
• trente sounds roughly like tront
• minutes sounds like mee-newt

The final s in minutes is normally silent.

The ç is called c cédille. It makes the c sound like s in front of a, o, or u.

So:

• leçon is pronounced with an s sound: leh/ luh-son
• without the cedilla, con would normally start with a k sound

The cedilla helps preserve the soft s pronunciation.

That is not the most natural way to say it for this meaning.

The most standard and natural sentence is:

• La leçon dure trente minutes

French normally uses durer to express how long something lasts.

They are used differently.

• durer is a verb meaning to last
• pendant is usually a preposition meaning for / during

Examples:

• La leçon dure trente minutes. = The lesson lasts thirty minutes.
• J’étudie pendant trente minutes. = I study for thirty minutes.

So in your sentence, dure is the correct choice because the lesson is the thing that lasts.

Not only that. Leçon can mean different kinds of lesson, depending on context:

• a class lesson
• a teaching unit
• a lesson learned from experience
• even a private lesson in some contexts

But in La leçon dure trente minutes, the most natural meaning is a lesson/class session that lasts thirty minutes.

Because French often uses the same basic order as English in simple statements:

subject + verb + time expression

So:

• La leçon = subject
• dure = verb
• trente minutes = duration

That is why this sentence feels quite straightforward for English speakers.