I think that some of the confusion possibly comes from the similarity in names - we've got Advocate, Advantage, Advantix....
Advocate has two active ingredients, Imidacloprid and Moxidectin. It treats fleas, mites, and lice, also most intestinal worms, and it is preventative for lungworm. It does not treat tapeworms or ticks. So whilst you are using Advocate, it is sensible to also use a wormer that does treat for tapeworms. Treating for ticks is a separate issue.
Advantage and Advantix both contain Imidacloprid. They treat fleas - the manufacturer claims that both of these kill at least 98% of fleas on a dog within 12 hours.
Advantix also contains permethrin which repels and kills ticks. This is fine for dogs, but this ingredient is highly toxic to cats - so if you have a cat in your household, and your dog socialises with the cat, then the manufacturer recommends that you don't use Advantix.
As all three of these products have Imidacloprid as an ingredient, you should not use more than one of them at a time.
I hope this helps a bit.