When you enter Brazil, before landing, you will be requested to fill in one Entry/Exit card. Good to have a pen in the hand baggage and following items are asked to be filled in; Name (as shown in passport), Purpose of the trip, Passport number or Travel document, Airline/Flight number, On arrival country of origin, Country of citizenship, Country where you live, Sex, and Date of birth. The card you will give to the immigration officials. They will stay with one part - meanwhile the other will be attached to your passport. When you leave Brazil, immigration officials will detach this from you passport. 

Make sure to not loose your part of the entry/exit card during your stay, if so, your return/departure can be delayed until immigration officials have checked your story. If you lost the document, ask for a new one at the check-in desk at the airport - then you avoid a boring situation with the federal police.