Final answer:
Time series data is a type of data where observations are recorded over a specific period of time and is characterized by trends, seasonality, and randomness. Cross-sectional variation is not a characteristic of time series data.
Step-by-step explanation:
Time series data is a type of data where observations are recorded over a specific period of time. It is characterized by the presence of trends, seasonality, and randomness. However, cross-sectional variation is not a characteristic of time series data.