I WONDER - How Was The Roman Army Structured?

The Roman army was a highly organized and effective military force. Each legion consisted of over 5000 soldiers and was led by a legette, often a governor or senator. Legions were divided into 10 groups called cohorts, which were further divided into centuries of 80 men each, led by a Centurion. This structured organization contributed significantly to the Roman Empire's successful expansion.

What were the smaller groups within a cohort called?

What was the role of a Centurion in the Roman army?