https://developer.apple.com/library/mac/#documentation/Porting/Concep...

Basically, for simpler programs, you distribute a .dmg file: it is a
disk image and it contains your app. Users simply drag the app and drop
it in the Applications folder. Often .dmg files contain also a link to
the Application folder so the user can drag the app and drop it to the
nearby link to easily copy it to the Application folder.

Here is a script that I use to create a .dmg file:

-- script start -------------------------------------------

#!/bin/bash

# change these
VOLUME_NAME="vvvP-1.1"
DMG_NAME=vvvP-1.1-i386.dmg

# this script creates a disk image for software distribution in the
current folder,
# copying the content from the app in the ../installed_cocoa folder

# Create an initial disk image (32 megs)
hdiutil create -size 32m -fs HFS+ -volname ${VOLUME_NAME} temp.dmg

# Mount the disk image
hdiutil attach temp.dmg

# copy files to the disk image
cp -R Applications /Volumes/${VOLUME_NAME}
cp -R ../installed_cocoa/vvvP.app /Volumes/${VOLUME_NAME}

# Unmount the disk image
hdiutil detach /Volumes/${VOLUME_NAME}

# Convert the disk image to read-only
hdiutil convert temp.dmg -format UDZO -o ${DMG_NAME}

-- script end -------------------------------------------