Mesa (a Spanish word for table) is a rock formation that looks like a table. A mesa is usually wide stable and the first stage of erosion.
Butte is a rock formation that is smaller and the second stage of erosion from a mesa.
Spire is the final stage of erosion from a butte. It is a rock formation that becomes narrow and free standing. Once eroded by wind and water, only the bottom Organ Rock that holds up the sandstone will remain.