Task vs. Ritual | Today vs. Tomorrow vs. Backlog

I’m confused on the details of the difference between these. Can someone help please? If I make a task today, if it is not completed will it roll over until tomorrow and the next day and so on if it isn’t completed? Or just disappear forever if I don’t do it? How can I make a task that stays until I do it? Same goes for tomorrow, if I make a task for tomorrow does it only last that day whether or not I finish it? And what’s the general difference between a ritual and a task? And what is a backlog even for? I thought I knew but then things I had loaded on went away and I didn’t finish them and can’t remember what they were.😣