This page talks about that…
As you’ll see, the vast majority of fan products we carry have wire lead terminations; there’s no knowing what connector a customer will want to use or the arrangement of the different wires within, so that’s most often left up to the end user. Cutting the leads + connector off an existing device and splicing them onto a replacement is also a trick that’s been done on more than one occasion…
There are a handful of connectors that are popular for fans, referenced in this post. This other post mentions several common in the PC industry.
“Molex” proper is a major manufacturer of interconnect product with perhaps 100K different products listed under that banner alone, so “molex connector” on this side of the screen has a meaning about as specific as “General Mills food”. The more common ones people have in mind when using the term are likely referenced in the above posts, but more generally will be found classified as rectangular connectors: in general, connector products with built-in contacts will be listed as “connectors” (possibly “connector assemblies”) while those with separate contacts get classified as “housings” of a type (rectangular, circular, etc.) and the corresponding contacts classified under the corresponding “contacts” family.
It may not be immediately apparent, but there -is- a method underlying the madness…