Someone in a writer’s group I belong to asked for the broad strokes’ definition.
Romans 10:9-10: “If you confess with your mouth that Jesus is Lord and believe in your heart that God raised Him from the dead, you will be saved.”
Don’t just read the verses and go “Wow, that’s all there is”, because that isn’t. It’s the salvation experience in a nutshell, but there is more to it than just believe and confess. Paul’s writings are never one-dimensional. You have to ask yourself what is means that “Jesus is Lord”, for example.
But it’s a good broad strokes answer to the theological question.