TASK Vs. EVENTS - when do you open each for a Lead and when to a potential ?

TASK Vs. EVENTS - when do you open each for a Lead and when to a potential ?

Could you please reply to these 5 questions, it's really urgent:

1. TASK Vs. EVENTS: While talking to a customer, when would you open a NEW Task and when do you open a new EVENT, and what is the difference between them ?

2. When do you create a TASK or an Event to a new lead ?

3. When do you convert a lead ?

4. When do you create a TASK to a potential ?

5. When do you create an Event to a Potential ?

Many Thanks,