Both field types are coming from Sitecore Experience Accelerator (SXA). You can find their implementation in Sitecore.XA.Feature.Taxonomy.dll precisely in Sitecore.XA.Feature.Taxonomy.FieldTypes namespace.
TagTreeList is used by "Tag Cloud" rendering.
This rendering looks like this (right column below Archive):
TagList is used by "Tag List" Rendering.
Renderings can be found in Sitecore under /sitecore/layout/Renderings/Feature/Experience Accelerator/Taxonomy in "master" database.
They are defined in Sitecore.XA.Feature.Taxonomy.config
by this config patch
<source patch:before="*[@namespace='Sitecore.Shell.Applications.ContentEditor']" mode="on" namespace="Sitecore.XA.Feature.Taxonomy.FieldTypes" assembly="Sitecore.XA.Feature.Taxonomy" prefix="content"/>
and also in "core" database in /sitecore/system/Field types/List Types/Taglist and /sitecore/system/Field types/List Types/Tag Treelist items.
Small details can be found here about renderings - https://doc.sitecore.net/sitecore_experience_accelerator/building_the_layout/renderings/the_sxa_renderings_and_rendering_variants#_Engagement
Both fields usage can be seen in really cool Alan Plocieniak's blog post -> https://alan-null.github.io/2017/12/sxa-blog#search-results-page.