To check here means to control, and to balance means to make things equal.
“Check”在这里是“制约”的意思，“balance”在这里是“平衡”的意思。
These checks and balances help control the three branches and keep them equal to each other.
“三权分立”既有助于控制这三个部门，又使其互相平衡。
If one branch tries to take too much power, one of the other branches can put a stop to it.
如果一个部门试图掌控太多的权力，其他部门可以制止。
The second important thing that the Constitution does is to guarantee (or promise and protect) the rights of all Americans.
宪法的第二大作用是确保所有美国人民的权利。
The representatives at the Constitutional Convention didn't want the government interfering too much in the lives of the people.
制宪会议的代表们不想让政府过多地干预人民的生活。
So they wrote a list of rights - a list of things that everyone could do - and made them part of the Constitution.
因此，他们写下了一系列人民可以做的事的权利清单——并使之成为宪法的一部分。
These are rights that the federal government guarantees.
这些权利是受联邦政府保障的。
The federal government is the national government, which makes laws for all of the states.
联邦政府是国家政府，它为所有州政府制定法律。
There are also state governments that make laws for each individual state.
各自的州政府也可以为本州制定法律。
The third thing the Constitution does is to define (or explain) what powers the states have and what powers the federal government has.
宪法第三大作用是界定了州政府和联邦政府所拥有的权力。
The states have to make laws that agree with the U.S. Constitution, since the Constitution is the supreme (or highest) law in the country.
各州制定的法律必须与美国宪法相符，因为宪法才是国家的最高法律。
译文为秀哈英语翻译，未经授权请勿转载！
