When you install applications in OS X, you usually download an installer in a .dmg image from the developer, in which there is either the program itself ready to be dragged into your Applications folder, an installation program to run from the disk image itself, or an installation package.
The later of these options will look like an orange box, and when double-clicked will launch the OS X installer program. This program will run you through the steps for installing the package contents, which is usually just a bunch of sequential information before you finally install the package.
In these steps, you will eventually see a progress bar, and then quit the installer to launch your program.
While this process usually goes without problems, sometimes it may be useful to see exactly what the installer is doing, including where files are being copied, and any any errors or warnings encountered with the installation process.
With the information in the installation log, you can see where a program and its components were installed, as well as when authentication (if any) was granted, and who the user was who installed the program. These may help you troubleshoot a faulty installation, or investigate how a program was installed on a system.
Quite useful tip. Thanks!
Also applications like fseventer can help: