Hi Jo
As Prof. John said it can be difficult to visualise descriptions of various items needed to manage the water and waste systems.
It might help if you browse an online catalogue such as
Towsure so that you can see for yourself the various items that are mentioned.
Many of these are also available second hand from online auction websites or Preloved where used items are advertised at fixed prices.
Waterhogs or Wastemasters (they are similar items) are not to be used for toilets, the toilet waste goes into the container of a cassette toilet and can only be emptied at a designated Elsan point on campsites or rally fields.
The clean water enters the caravan through a flexible pipe and pump, these should be supplied with your caravan.
The grey waste water exits the caravan via waste outlets on the offside or rear of the caravan, flexible pipe available from caravan accessory stores is used to connect the waste outlet to the water hog.
There is some good information for new caravanners
Here