Apps not fetched, X on icon?

Apple iPhone - Apps sometimes not fetched, X on each icon ?

Anyone know what the X on each app icon is supposed to indicate?

Occasionally a specific app does not launch after I touch it, but others do. Currently the Weather Channel app will not launch. If I press the icon a little longer the icons wobble and a X appears on each.

iPhone Apps
Don't touch the x unless you want to delete that app. The jiggling icons allow you to move the icons around.

-----
Touching an icon for a few seconds will allow you to edit the home screen arrangement. You'll know you're in this mode when the icons "wobble" and x marks on each icon (except default apps) appear.

Touching the "x" on an icon deletes the app from your iPhone. You can also drag the icons around to rearrange them. Also, dragging an icon on top of another lets you create a folder.

Pressing the home button exits this mode.

-----
...and moving an icon from one page to another (drag it 'past' the right or left edge) rearranges them across pages. Much easier to do this last action from iTunes however.

-----
I understand the moving icons and delete icon now. Any idea why some icons do not launch the app and a few minutes later, they do?

-----
When searching a list of apps in the App store, some apps have a small icon of a white plus sign in the upper left hand side next to the price. Does anyone knows what that means?

-----
I believe that means the program will work on the ipad as well. It will have the full ipad functionality.