know what (one) is about

know what (one) is about

To be adequately prepared or knowledgeable enough to do something; to be confident in one's abilities. You couldn't find a better leader: he knows what he's about, he stands up for his values, and he isn't afraid to put the wellbeing of others ahead of his reputation. I know her strategy may seem unorthodox, but trust me—she knows what she's about.
See also: know, what
Farlex Dictionary of Idioms.

know what you are about

be aware of the implications of your actions or of a situation, and of how best to deal with them. informal
1993 Ski Survey He ran a 3-star guest house before this, so knows what he is about.
See also: know, what
Farlex Partner Idioms Dictionary

know what you’re ˈdoing/aˈbout

(informal) have experience of doing something and therefore understand it fully: ‘I’m worried about David using that machine.’ ‘Don’t worry. He knows what he’s doing.’
See also: know, what
Farlex Partner Idioms Dictionary
See also:
  • know what you are about
  • know what you're doing/about
  • know what (one) is doing
  • know what (one) is talking about
  • know what you're talking about
  • know a thing or two
  • get with
  • get with (someone or something)
  • get with it
  • get with someone