docs: Add more information about the tool and some instructions

README.md

@@ -2,4 +2,19 @@
 
 > docker but simpler
 
-Usage: `miniroot -root "/opt/something" -workdir "/usr/src/app" -init "/usr/loacal/bin/npm start"`
+In contrast to Docker, miniroot **does not**:
+- have a concept of images and layers
+- isolate networks
+- handle volumes or bind mounts
+- have a central daemon
+
+It's just a simple tool that utilises namespaces to run applications in a semi-isolated environment.
+
+### Usage
+
+- get rootfs (you can use `docker export container_name > export.tar` for that)
+- extract it somewhere
+- run miniroot; example:
+```
+miniroot -root "/opt/something" -workdir "/usr/src/app" -init "/usr/local/bin/npm start"
+```