Peak periods refer to times of the year when there is an increase in demand for goods and services. This is usually seen during the holiday season, when people are shopping for gifts. UPS and HIGHS are two acronyms that are used to describe peak periods. UPS stands for 'United Parcel Service' and is a global package delivery service. HIGHS stands for 'High Intensity Growth Seasons' and is used to describe the periods of the year when there is an increase in consumer spending.