@AyanB214,
Some of these questions are answered in my reply in the other thread here:
An Ad Campaign is a set of advertisements all focused on one subject or message. You can think of it as a container of all ads from a specific company or brand. An ad is simply the advertisement itself.
You can track the ads you’ve seen by going to Settings --> Brave Rewards --> Ads --> 7-day ad history. You can also up/downvote them which will help train the browser on what you want (or don’t want) to see advertised.
Regarding:
So does that means yesterday my luck was good but Today my luck is very bad?
It’s also worth noting that there is a max number of ads (a cap) one can see each day, which I believe is currently 40. So there may also be times where you see tons of ads in the beginning of the day, hit your cap mid day, and then don’t see any others for the rest of the night.