diff --git a/README.md b/README.md
index 91f8e86e..b412d1bb 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,7 @@ can use a Makefile to export your KiCad PCBs just as needed.
 
 For example, it's common that you might want for each board rev:
 
-* Check DRC one last time (use [KiCad Automation Scripts](https://github.com/INTI-CMNB/kicad-automation-scripts/))
+* Check ERC/DRC one last time (using [KiCad Automation Scripts](https://github.com/INTI-CMNB/kicad-automation-scripts/))
 * Gerbers, drills and drill maps for a fab in their favourite format
 * Fab docs for the assembler
 * Pick and place files
@@ -21,6 +21,80 @@ As a side effect of providing a scriptable plot driver for KiCad, KiPlot also
 allows functional testing of KiCad plot functions, which would otherwise be
 somewhat unwieldy to write.
 
+## The configuration file
+
+Kiplot uses a configuration file where you can specify what *outputs* to
+generate. By default you'll generate all of them, but you can specify which
+ones from the command line.
+
+The configuration file should be named **.kiplot.yaml*. The format used is
+[YAML](https://yaml.org/). This is basically a text file with some structure.
+
+### The header
+
+All configuration files must start with:
+
+```
+kiplot:
+  version: 1
+```
+
+This tells to Kiplot that this file is using version 1 of the format.
+
+### The *preflight* section
+
+This section is used to specify tasks that will executed before generating any output. The available tasks are:
+
+- `run_erc` To run the ERC (Electrical Rules Check). To ensure the schematic is electrically correct. 
+- `run_drc` To run the DRC (Distance Rules Check). To ensure we have a valid PCB.
+- `update_xml` To update the XML version of the BoM (Bill of Materials). To ensure our generated BoM is up to date.
+ 
+The `run_drc` command has the following options:
+- `check_zone_fills` Every time we run the DRC the zones are filled again. This option saves the PCB to disk updating the zones.
+- `ignore_unconnected` Ignores the unconnected nets. Useful if you didn't finish the routing.
+
+Here is an example of a *preflight* section:
+
+```
+preflight:
+  run_erc: true
+  update_xml: true
+  run_drc: true
+  check_zone_fills: true
+  ignore_unconnected: false
+```
+
+### The *outputs* section
+
+In this section you put all the things that you want to generate.  This section contains one or more **outputs**. Each output contain the following data:
+
+- `name` a name so you can easily identify it.
+- `comment` a short description of this output.
+- `type` selects which type of output will be generated. Examples are *gerbers*, *drill files* and *pick & place files*
+- `dir` is the directory where this output will be stored.
+- `options` contains one or more options to configure this output.
+- `layers` a list of layers used for this output. Not all outputs needs this subsection.
+
+The available values for *type* are:
+- Plot formats:
+-- `gerber` the gerbers for fabrication. 
+-- `ps` postscript plot
+--`hpgl` format for laser printers
+-- `svg` scalable vector graphics
+-- `pdf` portable document format
+-- `dxf` mechanical CAD format
+- Drill formats:
+-- `excellon` data for the drilling machine
+-- `gerb_drill` drilling positions in a gerber file
+- Pick & place
+-- `position` of the components for the pick & place machine
+- Documentation
+-- `pdf_sch_print` schematic in PDF format
+-- `pdf_pcb_print`PDF file containing one or more layer and the page frame
+- Bill of Materials
+-- `kibom` BoM in HTML or CSV format generated by [KiBoM](https://github.com/INTI-CMNB/KiBoM)
+-- `ibom` Interactive HTML BoM generated by [InteractiveHtmlBom](https://github.com/INTI-CMNB/InteractiveHtmlBom)
+
 ## Using KiPlot
 
 You can call `kiplot` directly, passing a PCB file and a config file: