exercise/assignment difference

Introduction.md

@@ -12,9 +12,11 @@ Official terminology of ReCodex which will be used in documentation and within c
 ### Web Application (web-app)
 Graphical frontend of the whole ReCodex. This part is used by teachers and students.
 
-* **Exercise/Assignment** - Teachers are creating exercises which are solved by students. When exercise is solved then students submit their solution, this solution with all other informations (needed by worker) is called submission.
+* **Exercise** - Exercise is basic point of all evaluation. Students are receiving assignment from their teacher, but firstly there has to be authors of exercises from which assignments are derived. Assignment is basically exercise which was assigned to some group of students for evaluation.
 
-* **Sample solution** - When teachers create exercise, they should provide sample solution. This solution should pass all test cases in specified limits. It can be also used for auto-calibration of exercise.
+* **Assignment** - Teachers are creating assignments from exercises which are solved by students. When assignment is solved then students submit their solution, this solution with all other informations (needed by worker) is called submission.
+
+* **Sample solution** - When authors create exercises, they should provide sample solution. This solution should pass all test cases in specified limits. It can be also used for auto-calibration of exercise.
 
 * **Submission** - Submission is one solution of given exercise, it is sent by student to frontend of ReCodEx. To this term we can include all additional information about source code or submitter.