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.
The term "rendering" is most commonly used when describing the general exporting of a file, when encoding or exporting is actually the more precise terminology. In Premiere Pro, rendering relates more to the creation of preview files (the Sequence menu provides a command to "Render In to Out," for example. Rendering video previews come into play when playing back complex effects, or any effects beyond the capability of a system's real time capabilities. After Effects compositions that are exported are commonly referred to as "renders" too.
I hope this explanation helps clarify this common question.