行 (xíng) has two main uses: as a verb meaning 'to walk' (more formal/literary than everyday 走 zǒu), and as an adjective meaning 'OK, acceptable' or 'capable' (colloquial, like 好 but specifically for permission or competence). As 'OK', it's often used in the pattern 行不行 to ask 'Is it all right?'. It is not used for 'good' in a general sense — that's 好.