B1
一边…一边… — two things at once
How Chinese pairs simultaneous actions with 一边…一边, why both halves need the marker, and what to use instead when the two things are descriptions rather than actions.
Two actions, one person, at the same time. Each verb takes its own 一边.
他一边走一边打电话。
Tā yìbiān zǒu yìbiān dǎ diànhuà.
He walks along talking on the phone.
我喜欢一边吃饭一边看电视。
Wǒ xǐhuan yìbiān chīfàn yìbiān kàn diànshì.
I like eating in front of the television.
一 takes its usual tone shift — yìbiān — and in speech the 一 often drops entirely, leaving 边…边, which is quicker and very common.
别边走边看手机。
Bié biān zǒu biān kàn shǒujī.
Don’t look at your phone while you’re walking.
Actions, not qualities
The pattern joins things you do. Two descriptions of how something is want 又…又 instead.
他一边高一边瘦。
他又高又瘦。
高 and 瘦 are not activities you can be engaged in simultaneously — they are descriptions, and 一边 has nothing to attach to.
One subject, both halves
Both actions belong to the same person. Two people doing two things want an ordinary pair of clauses.
他一边看书一边听音乐。
Tā yìbiān kàn shū yìbiān tīng yīnyuè.
He reads while listening to music.
Against 着
着 also joins two verbs — 躺着看书, read lying down — and the difference is which one is the main event. With 着, the first verb describes the manner of the second and the second is what is happening. With 一边…一边, both are happening and neither is subordinate.
躺着看书 is reading, done lying down. 一边吃饭一边看电视 is genuinely both, and either could be the reason you are there.