In Germany there are 6 tax classes, and the tax class you fall into will affect the tax rate you are taxed at
Helpful Tips :
If a married couple have almost the same income it is always better to have tax class 4 for both spouses.
If a married couple, one spouse is earning alot more than the other or one is not earning at all. The spouse with high income should be on class 3 and the other spouse on class 5.
A married spouse with a spouse living abroad should be on class 1