The reason for the meeting, clearly stated in the emails, is that Trump Jr. was hoping to learn damaging information on Hillary Clinton. Someone else mentions the Russian government, to which Trump Jr. makes no response. It's unknown whether the person that mentioned the Russian government was speaking the truth, repeating an unfounded rumour, or just making it up.

In any case, there's NO EVIDENCE OF COLLUSION THERE. Nor, so far, is there any evidence anywhere that the Trump campaign colluded with the Russian government. There was contact between the Trump campaign and various Russians, but that's not a crime.