diff --git a/book/source/04-certificates.md b/book/source/04-certificates.md
index b658093..62f6c6c 100644
--- a/book/source/04-certificates.md
+++ b/book/source/04-certificates.md
@@ -465,6 +465,10 @@ To deal with this reality, the rpm-sequoia implementation was adjusted to accept
 
 #### Autocrypt
 
+The [Autocrypt](https://autocrypt.org/) project describes itself as:
+
+> [..] a set of guidelines for developers to achieve convenient end-to-end-encryption of e-mails. It specifies how e-mail programs negotiate encryption capabilities using regular e-mails.
+
 The Autocrypt Level 1 specification defines a specific [minimal format for OpenPGP certificates](https://autocrypt.org/level1.html#openpgp-based-key-data) that are distributed by the autocrypt mechanism.
 
 One goal of the Autocrypt mechanism is to distribute certificates widely. To this end, Autocrypt sends certificates in mail headers, where smaller size is greatly preferable.