Writers use direct characterization by revealing a characters personality. The writer has to say the characters personality directly.
Example: "The boy was very shy but very funny."
This sentence tells us the boy is funny but shy.
Direct and indirect characterization can easily get confused. Indirect is basically what we judge the character to be. Like appearance, actions and words.
Example: I see that Shaun isn't very smart because he fails all his exams.
Hopefully this makes sense and I helped. Good luck :)