Customised Installation - PosiEd

In the context of Salesforce orgs, the term “customised” refers to any changes to the configuration of the system which occur outside the Salesforce package used to build your system. We are not referring to the addition or deletion of data, but to configuration and setup changes performed after the installation, to enable requirements not found in the package.

The rule of thumb is that the fewer customisations you can get away with, the better, because of the implications for what happens when you upgrade, install new packages, or introducing other standard functionality. It is possible that you won't be able to upgrade using the standard process, or that the customisations you have added will be permanently lost. Please read Upgrades for more details about the upgrade process.