How to start an application using Android ADB tools

adb shell
am start -n com.package.name/com.package.name.ActivityName

Or you can use this directly:

adb shell am start -n com.package.name/com.package.name.ActivityName

You can also specify actions to be filter by your intent-filters:

am start -a com.example.ACTION_NAME -n com.package.name/com.package.name.ActivityName 

It's possible to run an application specifying the package name only using the monkey tool by follow this pattern:

adb shell monkey -p your.app.package.name -c android.intent.category.LAUNCHER 1

The command is used to run the app using the monkey tool which generates random input for the application. The last part of the command is an integer which specifies the number of generated random input for the app. In this case the number is 1, which in fact is used to launch the app (icon click).