Hello Khoi,

Here I suggest you some blogs links, I hope this will helps to clear workflow concepts.

This will give you full details of workflow in v8 and v10 both:
http://bloopark.de/en_US/blog/the-bloopark-times-english-2/post/odoo-10-workflows-partial-removal-265

https://www.odoo.com/documentation/8.0/howtos/backend.html#workflows

https://www.odoo.com/documentation/9.0/howtos/backend.html#workflows

https://www.odoo.com/documentation/10.0/howtos/backend.html#workflows

Thanks