This document discusses various metrics used for assessing research outputs and impact. It describes journal impact factor, which measures the average number of citations to recent articles published in that journal. It also discusses author-level metrics like the h-index, g-index, and i10-index, which measure an individual researcher's productivity and citation impact. These metrics are useful for tasks like grant allocation, benchmarking, hiring, promotions, and reviewing faculty/departments. However, no single metric should be considered in isolation as results can vary depending on the database or time period used.