filters r java classes which is intercept the client request
before it access a resource in server,then it intercept
server response before its reach clint

request filter

for security

response filter

compresed data

init(),do filter(),destroy are methods of filter

The ans cudhave been more precise: let me try :)
The filters are basically used when we need to change the
response sent back to the client like implementing
restrictions to few of the resources dependent on the user
who logs in like we dnt need to show few pages to few users
from a website then we need to make that logic in a new
class which implements filter interface and need to write
down the logic in the dofilter method which takes the
response and request objects which can be altered and
changed and the object of this class can be called dependent
on the condition of met on which we want to implement the
restrictions.

We can also use this interface to change the behavior of the
response.