Learn Hardcore Russian: Я прочитал конспект после урока.

Because конспект is the direct object of the verb прочитал. In Russian, direct objects take the accusative case. Since конспект is an inanimate masculine noun, its accusative form is identical to the nominative.

What does конспект mean in this sentence?

Here конспект refers to the set of notes or summary you make during or after a lesson. Think of it as your handwritten outline of what was covered in class.

What does the ending “-л” in прочитал tell us? How would it change for different speakers?

The “-л” ending marks past tense, masculine singular, perfective aspect.

A female speaker would say прочитала (adds “-а”).
For plural subjects (we/they) it becomes прочитали.
So you know from the ending that a man is speaking here and that he completed the action.

Why use the perfective verb прочитал instead of the imperfective читал?

Russian has two aspects: perfective for completed actions and imperfective for ongoing or habitual actions.

Я прочитал конспект means “I finished reading the notes.”
Я читал конспект would mean “I was reading the notes” (ongoing) or “I used to read the notes” (habitual).

Why is урока in the genitive case in после урока?

The preposition после (“after”) always requires the genitive case. Thus урок (nominative) becomes урока in после урока, literally “after the lesson.”

There are no words like “the” or “a” here—how does Russian handle articles?

Russian doesn’t use articles. Definiteness or indefiniteness is understood from context. If you really need to emphasize “this” or “some,” you’d supply a demonstrative (этот) or an adjective (какой-то), but ordinary sentences simply omit articles.

How do I say “my notes” instead of just “notes”?

Typically you use the reflexive possessive свой when the subject owns the object:
Я прочитал свой конспект после урока.
You could say мой конспект, but свой is more idiomatic in this kind of sentence.

Can I change the word order, and what effect does it have?

Yes. Russian word order is quite flexible. For example:

Конспект я прочитал после урока (emphasizes конспект)
Я после урока прочитал конспект (emphasizes the time “after the lesson”)
The core meaning stays the same; only the focus or nuance shifts.

Are there synonyms for прочитал, such as прочесть, and what’s the difference?

Yes. Прочесть is a perfective synonym of прочитать, but it’s a bit more formal or bookish. You’d see прочёл статью in writing, for instance. Another related verb is перечитать (“to read again”). For everyday speech about a first, completed reading, прочитал is most common.

Could I say после занятия instead of после урока, and what’s the difference between занятие and урок?

You can.

Урок usually means a school lesson (especially in primary/secondary school).
Занятие is a more general term for any class, session, or meeting (university lectures, club activities, gym sessions, etc.).
In both cases you’d use genitive after после (→ после занятия, после урока).