Clarify shell vs boot in man page

In retrospect it seems like this should have been obvious but it
confused me. Thanks to Daan for pointing it out on Matrix. Reword to
help out people like me in the future.

diff --git a/mkosi/resources/man/mkosi.1.md b/mkosi/resources/man/mkosi.1.md
index bbce44b578a6545d0f091b1e21318deb365d4f07..088d309f56d4e5870550d6bf2d25c64867665f2c 100644 (file)
--- a/mkosi/resources/man/mkosi.1.md
+++ b/mkosi/resources/man/mkosi.1.md
@@ -76,17 +76,18 @@ The following command line verbs are known:
 
 `shell`
 :   This builds the image if it is not built yet, and then invokes
-    `systemd-nspawn` to acquire an interactive shell prompt in it. An optional
-    command line may be specified after the `shell` verb, to be invoked in place
-    of the shell in the container. Use `-f` in order to rebuild the image
+    `systemd-nspawn` to run an interactive shell in the image. This doesn't
+    require booting the system, it's like a better chroot. An optional command
+    line may be specified after the `shell` verb, to be invoked in place of the
+    shell in the container. Use `-f` in order to rebuild the image
     unconditionally before acquiring the shell, see below. This command must be
     executed as `root`.
 
 `boot`
-:   Similar to `shell`, but boots the image using `systemd-nspawn`. An
-    optional command line may be specified after the `boot` verb, which
-    can contain extra nspawn options as well as arguments which are passed
-    as the *kernel command line* to the init system in the image.
+:   Similar to `shell`, but instead of spawning a shell, it boots systemd in the
+    image using `systemd-nspawn`. An optional command line may be specified after
+    the `boot` verb, which can contain extra nspawn options as well as arguments
+    which are passed as the *kernel command line* to the init system in the image.
 
 `qemu`
 :   Similar to `boot`, but uses the configured virtual machine monitor (by