Honorific (respectful) form of 'to see' (見る). Used to show respect toward the person performing the action; common in formal speech (e.g. 'please look').
どうぞ資料をご覧なさってください。
Please take a look at the materials.
先生は窓の外をご覧なさった。
The teacher looked out the window (honorific).
お時間があれば、私の作品を一度ご覧なさっていただけますか。
If you have time, could you please take a look at my work?