The terms rendering, exporting, and encoding are often used interchangeably, though technically, they have slightly different meanings.
For the purposes of this article, we'll use the term "export" when we're speaking about outputting a file to your computer. Here's why.
When discussing the term "export," we are referring to the overall process of outputting a file for export. This involves: a) preparing video effects that were applied to clips and b) the actual encoding of the file, where the file's codec is translated to a wholly new codec. These processes combine to form the exported file. The GPU & CPU work in tandem in the overall export process. The GPU, if enabled in File > Project Settings will speed up the export process for effects like Lumetri, Warp Stabilizer, even common scaling.
When discussing the term "encode," we are referring only to the codec translation process. The encoding part of the export process primarily uses the CPU. In After Effects, the act of exporting a file is referred to as rendering. Furthermore, the act of encoding is also referred to as rendering. Those that use both Premiere and After Effects tend to use all these terms interchangably, but wrongly, which can be confusing.
When using the term "rendering" and Premiere Pro, that process actually relates more to the creation of preview files rather than the exporting of files. Rendering video previews are commonly meant for playing back complex effects.
I hope this explanation helps clarify this common question.