Learn Hardcore Chinese: Lǎoshī xiān jièshào jīntiān kè de nèiróng, zài gàosu wǒmen měi gè bùfen de zhòngdiǎn. - The teacher first introduces today’s lesson content, then tells us the key points of each part.

了 often marks a completed action or a change of state. In this sentence, we are describing the usual or planned sequence of the lesson, not reporting a specific completed event.

So the sentence is more like:

“The teacher (will / usually) first introduces … then tells …”

If you were talking about a specific class that already happened, you might say:

老师先介绍了今天课的内容，再告诉了我们每个部分的重点。
(sounds like a report of what happened in one particular class)

But even then, Chinese often omits the second 了, or both, if the order is already clear from context. The given sentence is naturally read as general/habitual or as a plan.

Why is it 今天课的内容 instead of 今天的课的内容? Are other versions possible?

All of these are grammatically possible, but they differ in how natural they sound:

今天课的内容 ✅ (in the sentence)
今天的课内容 ✅
今天的课的内容 ⚠️ grammatical but clunky / heavy
今天课内容 ✅ more concise, also used

What’s going on:

今天课 or 今天的课 both mean today’s class/lesson.
内容 means content.
的 links a modifier to a noun.

So the structures are:

今天课的内容 → “the content of today’s class”
今天的课内容 → “the class content of today”
今天的课的内容 → “the content of the class of today” (a bit over-marked)

In everyday speech and writing, people often avoid stacking too many 的, so 今天课的内容 or 今天的课内容 are preferred. The version in the sentence is very natural.

What does 课 mean here exactly: class, lesson, or course?

课 (kè) is flexible and can mean:

a class session (“this period of class”)
a lesson (“this lesson’s material”)
a course (in some contexts)

In 今天课的内容, the most natural reading is:

“the content of today’s class/lesson”

It refers to what the teacher is going to teach in this particular class meeting.

What is the role of 的 in 课的内容 and 部分的重点? Why do we need it?

的 (de) links a modifier (an adjective or noun phrase) to the noun it describes.

课的内容
- 课 modifies 内容
- literally: “the class’s content” / “the content of the class”
部分的重点
- 部分 modifies 重点
- literally: “the part’s key points” / “the key points of a (each) part”

Without 的, these would either sound wrong or change meaning. In these phrases, 的 is doing what ’s or of does in English.

Why is 个 used as the measure word in 每个部分? Could I just say 每部分?

个 (gè) is the most common and general measure word in Mandarin. 部分 (bùfen) is a noun meaning part/section, and it is very natural to count parts with 个:

一个部分 – one part
每个部分 – each part

You can say 每部分; it is grammatically correct and also used. The difference:

每个部分 – slightly more colloquial and explicit; very natural in speech.
每部分 – feels a bit more compact or written, though still fine in speech.

In beginner and everyday contexts, 每个部分 is a good default.

What is the difference between 介绍 and 告诉 in this sentence?

Both involve giving information, but they’re used differently:

介绍 (jièshào) – to introduce; to present; to give an overview
Here: 介绍今天课的内容 = “give an overview / introduce today’s lesson content”
告诉 (gàosu) – to tell; to inform
Here: 告诉我们每个部分的重点 = “tell us the key points of each part”

So the sequence is:

First, the teacher introduces what the class will cover in general (内容).
Then, the teacher tells the students what the key points (重点) of each part are.

You normally wouldn’t say 告诉内容; content is usually 介绍-ed, not 告诉-ed.

What’s the difference between 内容 and 重点?

They refer to different aspects of what is taught:

内容 (nèiróng) – content
All the material covered: topics, explanations, exercises, etc.
重点 (zhòngdiǎn) – key point(s); main point(s); focus
What is most important to understand, remember, or pay attention to.

So:

课的内容 – everything that will be covered in the lesson.
每个部分的重点 – the important points within each section of that content.

Why is 今天 placed before 课 (as 今天课) instead of at the very beginning of the sentence or after 老师?

Chinese allows several positions for time words like 今天 (today):

今天老师先介绍课的内容……
老师今天先介绍课的内容……
老师先介绍今天课的内容…… ✅ (your sentence)

All are possible; the nuance:

Putting 今天 before 课 (→ 今天课) makes “today’s class” into a single idea: 今天课.
Putting 今天 after 老师 or at the start highlights the time for the whole sentence more explicitly.

Here, 今天课的内容 neatly groups today’s class with content, focusing on this particular class’s content.

Could we omit 我们 and just say 再告诉每个部分的重点?

You cannot omit 我们 completely without changing the structure. You would need some object or restructure the phrase:

再告诉我们每个部分的重点。 ✅
“then tell us the key points of each part”

If you drop 我们, 告诉 would have no explicit object:

再告诉每个部分的重点。 ❌ unnatural as-is

You could instead say:

再讲每个部分的重点。 ✅
“then explain the key points of each part.”

Here 讲 (jiǎng) can take 每个部分的重点 directly as its object (what is explained), and the audience is implicit.

With 告诉, the listener (like 我们) is usually expressed.

Is 老师 the only word for “teacher” here? Could I use 教师 instead?

Both mean “teacher,” but they are used differently:

老师 (lǎoshī) – common, everyday word; what students call their teacher; very natural in spoken language.
教师 (jiàoshī) – more formal; refers to the profession of teaching (e.g., in job titles, statistics, official documents).

In this sentence, which sounds like classroom narration, 老师 is the natural choice:

老师先介绍今天课的内容…… ✅
教师先介绍今天课的内容…… ❌ sounds oddly formal and not like typical classroom talk.

Does this sentence describe present, future, or habitual action? How do we know without tense markers?

Chinese does not mark tense the way English does. This sentence could be:

Present/future plan:
“The teacher will first introduce … then tell us …”
Habitual description:
“The teacher first introduces … then tells us … (this is how class is usually run).”

Context decides. Because there’s no 了, no time word like 明天 (tomorrow), and the structure is generic, it most naturally sounds like:

a general description of how the teacher usually organizes the lesson, or
a plan for what will happen in today’s class (since 今天 is present-day).

Both readings are acceptable; the sentence itself is neutral about past vs. future and just states an order of actions.