Obedient comes from obey (verb). It means doing what someone else (normally someone in power, like a teacher or parent) tells you to.
"I expect all my students to be obedient and behave well in the classroom."
When someone is obedient, they are displaying obedience.
"I took my dog to obedience classes. We both learned a lot!"
Assertive comes from assert (verb), meaning to stand up for your own rights and wants.
"My son was quite assertive when he asked his boss for a pay rise."
"Even though the driver was aggressive and rude, I was assertive when challenging the fare."
Please email me with any questions firstname.lastname@example.org