At the university, you hand in your own texts and work and never something that others have done. Copying other people's work without indicating the source is not allowed.
In brief, academic honesty means that the work you submit for assessment has to be your own work and not the work of someone else. Copying is not allowed, and you have to use proper attribution and referencing when using the works of others. In many cases, you will be encouraged to collaborate with others to enhance your learning, for example on hand-in exercises. However, the final work which you hand in must be your own, and you are not allowed to lend someone else your work for copying. Finally, you should be aware that all university employees are obliged to report if they suspect that a student is attempting “deception during examinations or other forms of assessment of study performance”.
At the beginning of each course, students at the Department of Physics are informed about importance of academic conduct. More general information about academic conduct/integrity/honesty has been published by Lund University Libraries. There you can also find more information about an automatic system called Urkund, which may be used in some courses to detect plagiarism, as well as the official guidelines and regulations on plagiarism.
If you have any questions, or if something is unclear about what is allowed or not, ask your teachers.