Yep, it's inspired by COG as well as MBTiles, hence the name. Key differences are:

* like MBTiles it's agnostic to what individual tiles are. You can store vector data as SVG, Protobuf, raster PNGs, JPGs or even raw digital elevation models.

* It's not backwards compatible in the same way Cloud Optimized GeoTIFF is.

* It has a recursive index structure to avoid needing to load in huge indexes at once for large datasets (hundreds of millions of tiles).

* It is designed for remote HTTP range reads. If your application can instead directly access a filesytem, like on a mobile phone, MBTiles, which uses SQLite, is a more established solution.

The specification is open source on GitHub https://github.com/protomaps/PMTiles and is still evolving in response to user needs. I've created direct client support for Leaflet and MapLibre, and plan to work on OpenLayers next.

Ah, so it's a general tile addressable system, where the individual tiles might be vector data, rendered vector data, or raster data. For rendered or raster data, the advantage is that it's a single file, rather than eleventy billion little files and directories. For the vector data, it's a tiling system, which allows you to do the standard things for dropping/combining features as mbtiles, just as one container file.