TPM (Trusted Platform Module) is a special chip on a Librem laptop motherboard which provides some interesting security features. To best understand what it can do please read the following news articles from our blog, sorted by date:
https://puri.sm/posts/purism-integrates-heads-security-firmware-with-tpm-giving-full-control-and-digital-privacy-to-laptop-users/
https://puri.sm/posts/purism-collaboration-with-cryptography-expert-werner-koch/
https://puri.sm/posts/making-heads-more-usable-with-menus/
https://puri.sm/posts/demonstrating-tamper-detection-with-heads/
TPM is required for the PureBoot secure boot feature. All current models of Librem laptops are equipped with the TPM chip and are capable of utilizing PureBoot.