Я записал его имя в блокнот.

I wrote his name down in a notebook.

Breakdown of Я записал его имя в блокнот.

• я: I
• в: in
• его: his
• записать: to write down

Questions & Answers about Я записал его имя в блокнот.

Why is записал used here, and what does it mean exactly?

Записал is the past tense, masculine singular form of записать.

Here it means wrote down, noted, or recorded.

A few important points:

• за- is part of the verb and helps give the sense of writing something down
• -л marks the past tense
• the form записал shows the speaker is male

So:

• Я записал его имя в блокнот = a male speaker
• Я записала его имя в блокнот = a female speaker

Why is there no separate Russian word for down, like in English write down?

Because Russian often builds that meaning into the verb itself.

English uses a phrasal verb: write down.
Russian uses a single verb: записать.

So записать already includes the idea of to write down / note down, and you do not need an extra word for down.

What does его mean here? Is it his or him?