What is Sabbath Day?

I have a question and i was wondering if someone can help me with this, What is Sabbath day and what do you do on a Sabbath day. Beecause i thought that on a Sabbath you cant work, but i'm 17 and since i'm 17 i go to school and is Homwork considered work? so does that mean no homework on Sabbath day? and what day is Sabbath day, is it Sunday or is it any day you choose. And What happens lets say on a Saturday where i end up procrastinating on my Homework and i start doing my homework at 11 PM and i can not finish it before 12 AM when its considered the next day, well i didnt do any work on saturday so can i consider Saturday my rest day and do my Homework on Sunday or am i doing evrything wrong?

Please someone correct me on this

Thank you much.

Forget the formality of which day of the week is "the Sabbath." Just throw that right out.

Jesus Christ is Lord of the Sabbath: He is our Sabbath. He is our Rest.

The idea is to cease from "your labors" and "your pleasures", etc., and labor in all things that are pleasing unto the Lord.

If that means doing your homework every single day of the week then do it and don't be a sluggish do-nothing. However, don't let this stuff interfere or hinder your study of the word of God and devotion to prayer.