The EU Blue Card is created for citizens of non-EU states that want to work in a EU state.
There are two different ways to apply for it:
You have proof about a university degree. If the degree was not obtained in Germany, the degree must be recognised in Germany.
You have an employment contract which includes a gross salary of minimum 47,600€. In so-called “shortage occupations” (scientists, mathematicians, engineers, doctors, IT) this gross minimum salary is lower (37,128€).
The residency permit due to the EU Blue card is limited up to four years (if your employment contract is valid for this time period). If the employment contract is set for a shorter time, the residency is valid for the duration of the employment status plus three months.
If you have worked in a highly skilled occupation for at least 33 months and have paid contributions into a pension fund you can be granted a permanent residence title.
If you have been in possession of an EU Blue Card for 18 months you may enter another EU Member State for the purposes of working in a highly skilled occupation without a visa and apply for the EU Blue Card for that country within one month of entering the country.
Furthermore you are entitled to live for up to twelve months in another EU state.
I hope, my answer will help you!