TDDDG
In short: The Telecommunications Digital Services Data Protection Act (TDDDG) governs data protection for telecommunications and digital services in Germany.
In more detail: It was called TTDSG until May 2024. The most important rule for websites is § 25: storing or reading information on the end device (cookies, local storage) requires consent unless it is technically necessary.
In Depth
See in detail cookie consent (TDDDG). Related: GDPR, ePrivacy Directive, tracking.
See also: Cookie-Einwilligung (TDDDG), ePrivacy Directive, GDPR (DSGVO)