In general, Task is something where in you will not know start time. Ex:- It is like a school teacher assigning some assignments to students. Teacher will not tell the student (or student will not know) when to start working on the assignment, but both will definitly know when it should be completed. On the other hand appointments will always have start and end time. Appointments are like meetings, demos, concalls, etc... where in you will have start time and endtime. Though Start time and end time may be tentative but still you will have some idea about them.
In general, Task is something where in you will not know start time. Ex:- It is like a school teacher assigning some assignments to students. Teacher will not tell the student (or student will not know) when to start working on the assignment, but both will definitly know when it should be completed. On the other hand appointments will always have start and end time. Appointments are like meetings, demos, concalls, etc... where in you will have start time and endtime. Though Start time and end time may be tentative but still you will have some idea about them.