Navigating

The UV Editor has a 2D cursor. Its position can be changed by LMB clicking in the UV editor. You can also manually adjust its position in the Sidebar region. The range by default is from 0 to 256 starting from the lower left corner. By enabling Pixel Coordinates, the range changes from 0 to 1.

2D View

Panning can be done by clicking the MMB and dragging.

Zooming can be done by scrolling Wheel up or down. Also, as in the 3D View, you can use NumpadPlus or NumpadMinus to zoom.

View Menu

Also see Navigating in the Image editor.

UV Local View

Displays only the UV faces that are assigned to the currently displayed image.

Display Other Objects

Displays the UVs of selected objects (Object Mode) in the background.

Display Texture Paint UVs

Hides the UVs in Paint Mode.

Frame Selected

Change view so that all selected uv vertices are visible.