Let me leave my comment here and explain quickly what is going on.
The reason: The president has been accused of commiting a crime of responsability, which basically means
that the government spent much more then it was allowed by the budget and that she kept lying over and over about that.
Non official reasons: There's a lot of other reasons for this vote to take place, but mostly those are:
1) because 2/3 of the country are for the impeachment, and bc her popularity is Under 10%
2) because she tried to protect lula against investigation (our former president and her biggest ally) by nominating him to be a minister. This is far worse then the principal reason, but they decided not to include this in the vote so they could start the process earlier, as this nomination happened after the start of the process.
3) because there's a massive investigation against corruption on-going in the country, many of the members of congress are under investigation opposition and gvt alike, they believe that by taking away the president they may save themselves.
4) it is said that the campaign for election was filled with irregularities on financement.
Position of the government: They refuse the idea that the manipulation of public spending is a valid argument for impeachment under our constitution, and that what is going on is a coup. They also defend the idea that the process has been made too quickly without following all of the processus correctly. A consequence of the impeachment will be the power transfer from the PT ("left wing", but not really) to the PMDB (center-right) because the vp is from another party; the defenders of the government say that they are worse, and truth be said, they probably are.
What will happen: The vote will very likely pass on the lower chamber of parliament by the 2/3rds needed and then by the 1/2 needed on the senate. After that the president is taken out of office for 180 days, further investigations will go on and then a final vote on the senate occur, if 2/3rds approve it, the president is taken out for good.
My position: I consider myself of centre left, and I'd defend the party on power if they weren't fucked up as they are. Their first years in power weren't bad for the country, and Brazil's left was considered a success by many left parties on the world, but the truth is that they were corrupt since the beginning, and got more greedy every year that passed, pillaging the country and sharing the spoils with other parties in congress that accepted to follow them.
I agree with some points of the government, the PMDB is worse then the PT, and this process under only the crime of responsability is probably too weak to pass. However the fact that the president decided to give a minister position to our former president in order to protect him from justice is absurd, and this fact is overly ignored by the governists, when it's clearly one of the worse crimes they commited.
I then support this impeachment, even if I think it could be better, it's the best for the country. I think the PMDB can't do worse then the gvt for now simply because they won't have political capital to do any shitty thing like giving the right for religious entities to put in question decisions of the supreme court (seriously, that bill was sponsored by many PMDB congressmen). The economy will probably go better without the current gvt with investors and consumers confidence rising, and someone being finally punished by the suffering of the country.
Sorry for that huge speech, but it's probably gonna help some to understand the situation. A good vid that explains it: https://www.youtube.com/watch?v=rFKsY5O7oYs