Tools and structure
A library is like a toolbox: you pick the tool for the job. A framework is more like a building frame: it sets the structure and gives you places to add your work.
Both handle common tasks. A date library might format a date; a web framework might organise how a website’s pages are built and shown.
Choosing shared code
Both can save time, but they also create a dependency. Teams consider maintenance, security, documentation, and how hard the tool would be to replace.
For browser interfaces, React, Vue, and Angular are often compared together even though they provide different amounts of built-in structure.