There are two analysis modes: Steady State and Transient.
The default selection, Steady State, causes the analysis to be independent of time.
Transient causes the analysis to be time-dependent. There are several transient parameters that define how a transient analysis will run.
It is possible to switch between the two modes during an analysis. Transient boundary conditions are applied on the Boundary Conditions dialog.
Note that all Motion analyses (rotating machinery and moving solids) are run as transient.