A wah pedal, also known as a wah-wah pedal, alters the tone and frequencies of your electric guitar to give it the distinct sound of someone saying "wah wah."
Filter pedals (also known as envelope filters) enhance your guitar tone by adding or taking away certain frequencies.
This is different from an EQ pedal as the filter pedal dramatically changes the tonal quality of your electric guitar.
Depending on settings, filter pedals can have a dynamic wah sound based on your playing dynamics, an "auto-wah" sound based on tempo settings or have what some refer to as a "fixed" or "cocked" wah sound.
Macdaddy Music sells a variety of wah and filter pedals from brands such as Dunlop, Electro-Harmonix, EBS, Source Audio, Xotic, and Keeley.