You've finished all those books about writing and you;re still trying to decide what to do. You're at a writer's group and you hear someone ask Are you a plotter or a panster?" You scratch your head wondering what they mean.
A plotter is someone who outlines their entire story before beginning to write.
A panster is someone who sits down and just writes.
I believe most writers begin as pansters. I know I did. My first book took years to write and it wasn't over 50,000 words. That's not a long novel but as I wrote and let my fingers fly I was telling a story and there were holes in the plot, deficiencies in the characters, almost no setting, dialogue with every character sounding like the other one. All these things were pointed out to me by editors who took the time to read the book. That was in the days of editors reading entire mss and making comments.
Suddenly it dawned on me that if I knew these things before I began the story the writing might go easier. That's when I began to look at matters before I began to write. I do envy people who can sit down and write the perfect story other than for a little revision but that will never be me. Though after all my years of writing most of the planning and plotting is done in my head.