Thank you for the opportunity to help you with your question!
The main difference is that ,for values of real GDP are adjusted for inflation while values of nominal GDP are not i.e REAL GDP = NOMINAL GDP/ DEFLATOR ; where deflator = 1+ inflation relationship between the real GDP and the business cycle?
Expansion phase - a sustained phase with a rising GDP Recessive phase - A sustained period in which GDP is falling. Thus a biness cycle is a series of expansion and contraction of GDP through peaks , expansion, troughs ,and rescession
Please let me know if you need any clarification. I'm always happy to answer your questions.