Conflict is your good ol’ problems, or struggles with characters or plot in story. It gives your story dimension and gives the reader something they want to read. No one wants to read a story about a perfect world, it’s just not that exciting, or realistic, honestly.
There are two types of conflict: internal and external.
Internal Conflict is a conflict that takes place inside the character. It’s their inner struggle with their emotions or morals that’s creating tension in the story.
For example, in the short story The Horse Dealer’s Daughter, the Doctor, Jack Ferguson, has an internal battle over whether or not he loves Mabel, the daughter of a recently deceased horse dealer, who is now left without any money or hope for a future.
External Conflict is conflict created by external forces. The external conflict in The Horse Dealer’s Daughter is when Mabel is drowning in the lake before the doctor pulls her out.
Think of conflict as the things that go wrong, which isn’t such a bad thing in storytelling. Without any conflict life would be rather dull. This is conflict in a nutshell, if you want any more information on it check out Plot & Structure.