一边…一边【yìbiān … yìbiān】

一边…一边 puts two actions side by side: the same person does both at the same time. Each 一边 goes straight before its verb, and the subject comes before the first one.

Actions, not descriptions

Each half is something a person does, and does over a stretch of time. Two adjectives don't fit; they take 又…又.

• × 他一边很高一边很帅 → 他又高又帅

One person doing both

The pattern needs a single subject. Two people doing different things at the same time take 的时候.

• × 我一边做饭，他一边看书 → 我做饭的时候，他在看书

边…边

With one-syllable verbs, 一 can drop out: 边吃边聊, 边走边说. It's short and common in speech.