In "Animal Farm", in what way do the animals act like animals? In what way are their ideas and words like humans?

The animals
look like animals, but that's about it.  They have the general life of animals (outside, what
they eat, etc.), but they are just ideas, or representatives of people.  For instance, they can
talk, train/capture other animals, lie, manipulate history for their own advantage and generally
have most of the qualities associated with the tyrants they represent.  So thepresents the ideas
of Marx and sets the stage for the "Revolution."  At no point does he seem to be an
animal, yet his not being a person helps us focus on the ideas rather than the person about whom
we may have strong opinions.  It's a great technique.  In your initial read it's fun trying to
figure out who the animals "represent," and in subsequent readings it's fun to find
the subtle little ways they really "are" these people.