Yang is the most frequent word in Indonesian after the pronouns, and beginner courses barely mention it because it has no single English translation.
Its job: take a description and turn it into a thing.
The one that
yang merah ‘the red one’
yang murah ‘the cheap one’
yang di sana ‘the one over there’
You met this in A1 without the explanation: ada yang lebih murah? is literally ‘is there one that is cheaper?’.
Saya mau yang itu. ‘I want that one.’
Yang mana? ‘Which one?’
Relative clauses
English uses who, which and that. Indonesian uses yang for all three, and never changes it for person or thing.
Orang yang tinggal di sini. ‘The person who lives here.’
Buku yang saya baca. ‘The book that I read.’
Motor yang saya beli kemarin. ‘The motorbike I bought yesterday.’
Note the last one has no equivalent of “that” in the English translation, because English drops it. Indonesian never drops yang.
Where English speakers go wrong
They leave it out, because English lets them.
Orang tinggal di sini is not ‘the person who lives here’. It reads as a sentence: ‘a person lives here’. Without yang, the description becomes a statement, and the whole sentence collapses.
This is the single most common structural mistake at this level.
Set phrases worth learning whole
Yang penting… ‘The important thing is…’
Yang jelas… ‘What’s clear is…’
Yang benar saja! ‘You must be joking.’
The first two open opinions constantly in conversation, and knowing them lets you buy a second while you assemble the rest of the sentence.
With adjectives, to be precise
Compare:
rumah besar ‘a big house’
rumah yang besar ‘the house that is big’, singling it out
The first describes. The second points. In speech the difference is often ignored, but in writing it is real.
What you’ll actually hear
Yang shortens to ng in fast casual speech, and in messages it is often written yg.
yg mana? ‘which one?’