ArcMap: Define Projection vs Project Tool
How & when to use Define Projection tool versus Project Tool, with background info about geographic data (geographic coordinate systems and projections) to understand what these tools do in ArcMap.
Part 1: Background
Understanding geographic data (Geographic coordinate systems, projections, and GCS/PCS): 0:18
How ArcMap behaves (data frame coordinate system, projecting on the fly): 1:38
Project tool vs. Define Projection: 2:58
Part 2: Doing it in ArcMap
Unknown Spatial Reference warning 4:00
Using the Define Projection tool 4:36
Data Frame Properties & Geographic Coordinate Systems warning 6:20
Using the Project tool 8:36
Recap: 11:30