The delinations between types opf software programs are blurring more each day.
Here’s a link to Wikipedia’s definition of content management systems.
Blog programs such as WordPress can be used as a CMS.
Blogging modules now exist for CMS programs that were not originally designed for blogging.
Photo gallery software that was once stand-alone has been modularized for use within blogging and CMS programs.
CMS programs are open source, others not.