Kodi is the free, open-source media center that turns any computer or TV box into a library player for your own files: movies, series, music, photos, with add-ons for streaming formats you configure yourself. Two decades of development and a huge community stand behind it.
It plays what you point it at and ships nothing of its own, so third-party add-ons are a trust decision you make. For local libraries, it is the standard.