What is Visio Pro for Office 365?

[JuneTheSecond]

It is my self answer to the forgotten question.
And I am not sure my answer is always correct.
1. What is Office 365?
365 means days in a year.
You can buy license for only one year. 
You can also buy license for only one month.
If you use Visio only to create a new year card, you buy at December 1, and end in December 31 every year.   

2. Do I need Office for Business, too?
No, You don't, if you wish to use only Visio.
Even though you need to use Excel or Word , you can use online Office.
Functions are restricted, but they are useful with many other applications.

3. I've bought Visio Pro for Office 365 and Office Pro Solo.
Were they wrong choise?
Yes, it was a wrong choice, because I do not use Excel or Word at all.
I have ended the license, as I was aware I was not using Word or Excel at all.