Multiple Chapters

Filler chapters should be fluffy or bring up something that can be easily resolved quickly. Comedy and Fluff are the best filler chapters, as normally they are never addressed again, only there to bring the mood up and distract the readers from the plot. The main character should be pulled in a crazy situation with their best friend or romantic partner and lead to a comedic ending. OR the character should stay with their romantic partner all day, cuddling, kissing, etc. They should spend the chapter doing nice things with loved ones. It's not a great idea to put angst in as a filler as you'll have to quickly resolve it since filler chapters are meant to be quick an easy. It's not recommended to address them later on, however, if you want to play 4D chess with you're readers, you can put a scene of actual plot importance in a filler chapter that doesn't seem important until later on it's brought up, but that requires a lot of plot mapping, and the ability to not jump the gun and write ahead or spoil it on accident. 

These chapters should be related to the plot previously summarized or introduced. Whatever is put in these chapters doesn't have to be addressed but it's better if you do instead of leaving loose ends for readers to pick apart. However, not every issue should be immediately addressed it makes a better plot if you leave certain things untouched for a while but eventually bring them up, reminding the readers that everything that you put in the story matters. The character should slowly progress through whatever challenge they're going towards, and their character growth. A story that moves slower will feel more real, but it's not uncommon for writers to not have patience and make it a fast-paced story, speeding up all of the above. Sometimes you just wanna finish the story and that's so real.