The word ‘filters’ in photography can have several meanings. Traditionally, a filter is an optical attachment for a lens that modifies the light entering the camera. These come in various types and include traditional round filters that screw directly to the filter thread on the lens, and square filter systems that use a filter holder and square filters that slide into slots in the holder.
You can also get a so-called low-pass filter in front of the sensor to prevent interference or moiré effects, and an infra red filter to restrict the light captured by the sensor to the visible spectrum.
‘Filters’ can also be effects applied in photo editing software or in smartphone apps.