I could be wrong, but you may be overthinking this.

Exposition, in layman's terms, is necessary background information a reader needs to learn to give context to the story, but which does not on itself drive the plot forward. It's not action; it's just information. It can be boring.

Likewise, my guess is that, by character factors, the blogger just means things about the characters that you need to know for story context.

When writing exposition, some advice you might encounter:

- keep it brief and concise
- break it up and spread it out
- "show, don't tell" as much as possible
- use flashbacks

For example, say we readers need to know that your detective joined the police force because he witnessed his mom's murder as a child, but the perpetrator was never caught and brought to justice. You could (1) use narrative to simply say that, like I just did, or (2) have this revealed using dialog in which the character bares his soul to someone else, or (3) use flashbacks to show us the character as a child experiencing different scenes - his discovery of the murder, a detective interviewing him as a witness, a press conference, dad and child grieving together at a gravesite, etc.