When deploying an OpenERP system, it is important to understand the various OpenERP versions as well as the release and upgrade policies. There are two major versions of OpenERP available: the stable version and the trunk version. The stable version is the standard support version of OpenERP and typically the one you should chose to install for most situations. The trunk version is the development version and will often contain bugs and unfinished features. It is primarily downloaded by developers or those wishing to get a look at the latest features.
The goal of the OpenERP development team is to release two stable version upgrades each year. OpenERP further labels some stable versions as Long Term Support (LTS) versions. These releases are supported by OpenERP for those that have an OpenERP Enterprise support contract. For any production environment, it is smart to choose an LTS version. Most importantly, installing an LTS release of OpenERP will make bug fixes and patches much easier to implement.