Let's say a story begins with an old man...say a retired factory worker who is set in his ways and harbors long held biases about the roles of men and women in marriage. His wife becomes ill and dies at the beginning of the story. The man becomes lonely, but he's unwilling to share those feelings with others, instead becoming cranky and reclusive. When his only daughter comes out of the closet and tells him she is marrying her same-sex lover, he is outraged and disowns her. Months go by with him refusing to answer or return her phone calls. She finally gives up.
One day, our depressed old man suffers a massive heart attack. Paramedics use CPR to keep him alive until the hospital can take over and he survives. He deeply appreciates a young paramedic who provided him with hope and encourangement during the ambulance ride. After regaining his strength, the old man drops by the fire station to personally thank the young lady paramedic. His daughter and her new baby happen to be there visiting with her "spouse". The baby is beautiful and reminds him of his daughter when his wife first held her. This awkward moment causes the old man to reassess his prior values. Not long thereafter, he and his daughter's family take a trip together to
Conflict drives stories. Why? Because it provides the tension that makes a story interesting. The old man's rigid value system resisted change...he even disowned his only daughter. Then, the baby broke through some invisible emotional barrier, causing the main character to undergo a fundamental change in his value system. That process of reacting to conflict is character development...and it was only made possible by the old man's initial characterization. Characterization is all the values and features of the character that will react to events in the story.
Pretty simple concept, huh? Then, why do so many writers struggle with the difference between character development and characterization?