置く (おく) means 'to put' or 'to place.' It's a transitive verb used when you intentionally position an object somewhere. The particle 'に' or 'へ' indicates the location. For example, 'ペンを机に置きます' (Pen o tsukue ni okimasu) means 'I put the pen on the desk.'

置(お)くは「置(お)く」という意味(いみ)です。物(もの)をどこかに置(お)くときに使(つか)います。「ペンを机(つくえ)に置(お)きます」