B1 is one of the CEFR levels described by the Council of Europe. You can practice reading, listening, grammar and vocabulary on this site.
The ability to express oneself in a limited way in familiar situations and to deal in a general way with nonroutine
Can ask to open an account at a bank, provided that the procedure is straightforward.
Can understand the main points of clear standard input on familiar matters regularly encountered in work, school, leisure, etc.
Can deal with most situations likely to arise while traveling in an area where the language is spoken.
Can produce simple connected text on topics that are familiar or of personal interest.
Can describe experiences and events, dreams, hopes and ambitions and briefly give reasons and explanations for opinions and plans.
B1 level exams
At this level you can do the PET and PTE General level 2 practice exams
You can also get an a B1 certificate if you do well enough in the PTE Academic, a multi-level exam, while B1 level candidates should get a band score of 4-4.5 on the IELTS test.
B1 level practice
This web site contains practice tests at B1 level for reading, listening, grammar and vocabulary.