Definition
To have a good understanding of how things work, especially in a specific area, and to be able to make sound judgements.
識途老馬
Despite his young age, he's been around in this industry for a while now, so he knows what's what.
儘管他年紀輕輕，但他在這個行業已經待了一段時間，所以他很清楚狀況。
Don't try to fool her; she really knows what's what and won't be easily deceived.
別想騙她；她真的很懂行，不會輕易被騙。
In negotiations, those who know what's what understand what's important and what can be overlooked.
在談判中，那些懂行的人知道什麼重要，什麼可以忽略。