瞧 is colloquial and especially common in northern Chinese/Beijing dialect. 瞧瞧 (qiáoqiao) is a casual 'take a look.' 瞧不起 (qiáo bù qǐ) = to look down on/despise.
register
瞧 has a warm, informal feel. It's used in spoken Chinese the way 'look here' or 'check this out' is used in English. 看 is the neutral/standard equivalent.
