What is progression?
Progression is a mod that allows you to control how a player can interact with the world, or the things they can craft, at the basic level. At the more involved level, it allows you to build and design tech trees, where a player cannot complete something until, something else is done. Be this action crafting an item, or collecting drops or more. You can also reward them for completing specific tasks, instead of restricting what they can do, if you so desire. Progression would also allow you to build class systems, restricting what certain groups of players can do, or give them abilities based upon their class. You could for example, forbid a group of people from ever being able to craft a furnace. While another group can build furnaces, but they walk much slower. You could also make custom shops, or a quest line. This is just a basic overview of the things you can do with progression. With it's requirements, conditions and results, you can create many more different systems than I have listed here, making it a very powerful tool for modpack makers.

How to get Started editing
To get started editing you will need to grab yourself the Progression Editor book, this book is where all the editing is done. For the most part it should be fairly obvious what you need to do, but there are a lot of tooltips that can help you out. If you have any issues feel free to ask. You can also take a look at the Progression section on curseforge, for some examples.

Edit Mode

Display Mode

Enchiridion Support (Requires 3.1.0+)
Progression also comes with some built in support for Enchiridion adding special features and actions, so that you can make better looking editors. As well as being able to place features individually it also comes with a template for a simple book mode, more for quests, where you can write out images and text to display if you wish to have more of a story to go along with your progression. Simply while in edit mode insert the HQM Clone template. While in edit mode you can then right click the open button, which will automatically generate the list of tabs, and opening them will automatically generate criteria, and opening them will generate the information pages. You can add and remove these elements, this is just the autogeneration to make things easier.

Templates
I'd strongly encourage to share and create your own templates, this is very simple, just for sharing tab templates press s while clicking the tab and for criteria you can find the save button in the criteria itself at the top. I'd recommend uploading your templates to the Progression section of curseforge which can be found here. I've created a few examples to get started.

Progression 1.7.10