One month of steemit and I still need expert's help!!

Helllllooooo people!!
Good afternoon from Bangladesh.
I'm Zafrin. I was born and brought up in Sylhet, a small but peaceful city of Bangladesh. About my studies, currently I'm taking CCNA(Cisco Certified Network Associate).
I have joined steemit.com last month and it was a very good experience here. Grateful to all steemians for their support.
I still have few questions about several terms of steemit. I hope you guys will help me out.
=> First question : What will happen if I choose 'decline payout' here?

=> Second question : What does it mean by power down?

=> Final one : What benefits I will get by transferring to savings?

Thanks in advanced!
💕💕