This package helps you creating custom blocks with little code and maintainability.
Usually it is a lot of work to create custom blocks for client requirements. Each time you need to create all the forms and implement all the logic behind etc. This add-on will easify that process a lot. And the best of it, you can change your blocks anytime you want.
To learn more, please read the documentation here: https://www.concrete5.org/marketplace/addons/tm-blocks/how-to-use-tmblocks/
There are some examples for concrete blocks on github: https://github.com/farion/concrete5-tmblocks-default (just copy one of the blocks out of the blocks folder into your project package)
Note: This add-on is for developers only. You have to write some PHP-Code to make your blocks work.