What drives your characters? Why do they have a particular goal? The answer is their motivation. A character with weak motivations isn't going to charm the reader into turning the pages. Not all the characters in a story will have motivations. The walk-ons won't for they're for a purpose and once they have served that purpose they won't be seen again. The hero, heroine, villain and vital minor characters should have strong motivations. Just what are motivations? A motivation is a reason.
There is the one concerned with self-preservation such as hunger, shelter safety, self-defense.
The need for love in all it's phases such as loyalty, sexual desires, loyalty, pity.
The adoration factor including things as gratitude, awe standards of right and wrong.
The power factor which is the desire to rule someone or many.
The social factor or the need to belong to a group including the herd factor and social considerations.
A character may have more than one of these motivating factors which makes for a complicated character. Usually one is the predominating motivating force that drives your character into action. Mary wants to have a child. John wants to control his spouse. Laura wants to escape the flood and fears for her safety.
Motivation can be shown in a number of ways. By the character's actions. By their speech. By the speech of other characters. By a character's thoughts. By the writer's statement.