'看一看' is a reduplicated verb phrase formed by repeating the verb 看 (kàn, 'to look') with the numeral 一 (yī, 'one') inserted in between. This structure softens the action, making it sound more tentative, polite, or casual — like 'take a quick look', 'have a peek', or 'just glance'. It’s not about duration but about intention: the speaker implies they’ll look briefly and without strong commitment.

This pattern is very common in spoken Mandarin and appears across many verbs (e.g., 想一想 'think for a moment', 试一试 'give it a try'). '看一看' often appears in requests ('Can I take a look?'), suggestions ('Let’s have a look'), or invitations ('Come see!'). It carries no inherent object — the thing being looked at must be specified separately (e.g., 看一看这本书 'take a look at this book'). Unlike the bare verb 看, 看一看 almost never functions as a command without context or politeness markers.