I have looked around but I cannot find exactly what is the purpose of the module:
I would like to disable it but I want to be sure what I am doing.
The module relates to the EU WEEE Directive (Waste Electrical and Electronic Equipment), but in Magento can actually be used for any products you need to apply a fixed tax amount to.
To cover your costs, it gives you the ability to setup FPT (fixed product tax) on products where you need to supply a service to the customer after purchase. In the case of WEEE, you are required to offer the customer a means by which to recycle their electrical items through you which will obviously cost your business a certain amount.
I'm not sure of the ramifications of disabling the module in terms functionality and tax calculations - you'll have to test that yourself, but if you don't sell any products which need a fixed product tax then you at least don't require the functionality the module offers.