Filters, multiple users - do the filters stay seperate?

I have a large release plan and our users would benefit from using filters to pull out information specific to their department or the product they are assigned. My questions are if we teach everyone how to use filters, and someone saves the sheet with the filter turned on (but the filter is not shared), does the next person who goes to view the release plan see the filter which the last person had used?

Or if the filters are not shared, does it not change the view of the sheet for everyone?

If the filter is not shared, does that simply mean that other people can't use it but it will still affect the sheet for everyone if the sheet is saved with the filter turned on?