How do I change the transparency of an ArcMap layer?

You can change the transparency of an ArcMap layer using the Effects toolbar. Here's how:

1. Activate the Effects Toolbar: Navigate to the main menu and click Customize > Toolbars > Effects.

2. Select the Layer: On the Effects toolbar, use the layer drop-down arrow to choose the layer you wish to make transparent.

3. Adjust Transparency: Click the Adjust Transparency button (it usually looks like a half-filled circle). A slider bar will appear. Drag this slider to adjust the layer's transparency. Moving the slider to the right increases transparency (makes the layer more see-through), while moving it to the left decreases transparency (makes the layer more opaque).

Essentially, the Effects toolbar provides a quick and easy way to control the transparency of your layers in ArcMap, allowing you to visualize overlapping features and underlying data more effectively.