This is pretty explanatory. Donald Trump Jr. is in some hot water as of late because of his contact with a Russian lawyer. He changed his story multiple time about why he met. The current one he is sticking with is that the lawyer was going to give him dirt on Hillary Clinton. This is illegal, even if no information came from it.
It is so strange that the Trump Administration has been so terribly bad about controlling this story. This is far from the first or last scandal during a presidency. But the fact that Trump’s people can’t manage to maintain this story or prevent it from continuing to develop makes them all look quite guilty.
Don Jr and the rest of Trump’s Administration have lied since they launched their campaign 2 years ago. You lie when you have something to hide. Each lie gives us clues and increases scrutiny, and ultimately will lead to the truth.