On the Vundle GitHub page it says that one should use
PluginInstall to install plugins, but when I search for Vundle on the web people often use
BundleInstall instead. Both commands seems to be available. Is there a difference, and what should be used when?
Commands with the word
Plugin should be preferred.
In past plugins used to be called "bundles", therefore all associated commands had "bundle" in the name. In the beginning of 2014 there was a global rename (see this commit). The old "bundle" commands were left only for compatibility reasons.