The Midair Spring Jump, commonly shortened to just Spring Jump, is one of the basic tricks used in Super Mario Maker. There are many variations of the basic midair spring jump.
How It Works
When Mario drops a spring at the peak of his jump it will land underneath his feet allowing him to jump off it in midair. The reason for this is because when Mario has horizontal momentum the spring is dropped straight down, instead of being dropped forward when he has none.