For better or worse, tenure evaluations are a crazy important part of academic life in the US. You have roughly five years to produce enough research of a high enough quality to earn the right to keep doing said research.

The three common metrics for evaluating are:

1. citations -- highly cited papers are evidence of contributing to academic society

2. impact factor -- papers published in highly selective journals that peer reviews submissions are considered better

3. money -- AFAIK nobody says this out loud, but if your department can't bring in revenue to support you and your researchers, your tenure case is on thin ice.