B1: the level German officialdom asks for
B1 is the level that appears again and again in German official life. It is where the state-funded integration course ends, and it is the language requirement that comes up when residence and citizenship are being decided. For most learners in Germany it is the target whether they chose it or not.
What B1 actually lets you do
At B1 you can deal with almost anything routine without switching to English - a landlord, a doctor, a bank, a parents' evening. You can describe what happened, give reasons for an opinion and follow a conversation about familiar things. Fast group talk and regional accents still defeat you.
How long it takes
German sits a category above Spanish and French for an English speaker - the vocabulary is close, but the cases and word order cost time. B1 usually takes somewhere around three hundred and fifty to four hundred and fifty hours, and the integration course is built to roughly that length.
The integration course ends here
The integration course, the Integrationskurs, runs to B1 and ends in the Deutsch-Test für Zuwanderer, which reports either A2 or B1 depending on how you do. It is heavily subsidised and in many cases obligatory, so for a great many people B1 arrives as an appointment rather than a choice.
When B1 is not the level you need
For university, B1 is not enough - degrees taught in German normally want C1, tested by TestDaF or the DSH. Residence and citizenship requirements sit lower and have been revised more than once, so confirm the current figure with the authority deciding your case rather than relying on any article.