One of the 16 personality types in the Myers-Briggs personality test aka Myers-Briggs Type Indicator ... MBTI ....
Go here for a greater description of the ISFJ personality type....
ISFJs are traditional, loyal, quiet, kind and very sensitive to other people's needs. They have rich inner thoughts and emotions. They value stability and cultural norms. They are very adept at giving attention to detail.
ISFJs are characterised above all by their desire to serve others, their "need to be needed." In extreme cases, this need is so strong that standard give-and-take relationships are deeply unsatisfying to them.
They are extremely loyal, kind-hearted, sensitive individuals who like to help others and make sure that others are taken care of and that people behave appropriately. They are often known to take other people's problems on their shoulders.
Due to their generosity, kind-heartedness and strong ethics to do the right thing by others, people naturally rely on them or take advantage of them. Their kind-heartedness is their biggest weakness as some people selfishly use them up, but their close friends are often there to support them or even stand up for them in such a time where the ISFJ feels unappreciated and taken advantage of.
ISFJs are the backbone of society and without their support, the world will fall apart. Everyone needs an ISFJ friend in their life. Just don't take advantage of them.
Marge Simpson is your typical ISFJ
Friend of an ISFJ:
"stop being so nice to people who treat you like shit, i hate seeing you get taken advantage of like this"
"but someone has to help them, if i don't then who will?"