What is the difference between Filter and Equalizer？

Simple answer - a filter 'filters' things - it removes frequencies from a file by cutting them, usually by an amount that can be varied. An equaliser can both both cut and boost frequencies and so even out unbalanced recordings. So a filter could be argued to be a sub-set of an equaliser. The best one to use in Audition, incidentally, is the parametric one, once you've got used to what it can do.

This might help

https://helpx.adobe.com/au/audition/using/filter-equalizer-effects.html

or even this from Mike Russell

https://www.youtube.com/watch?v=bGYr5Htr3SQ