Angel Srw Me,
Welcome to this beautiful site, first!
A suffix is a part of word, which is put in the end of a word or root. For example, if we have to use suffix ISM, we can make the following words -
Syllogism, Idealism, Realism, Existentialism...
Similarly, if we use the suffix LY, we can make the following words -
Slowly, Fastly, Really, Deeply, Apparently...
When you are asked to fill a suffix on a form, you are asked if there is any addition to your name like Younger (Yr.), Junior (Jr.), Senior (Sr.) or IV. For example, Pitt the Younger, Henry VII, Badal Sr. or Rubella Junior.
Let me tell you that there are two types of AFFIXES. An AFFIX is a word or word-root, which is either put in the end or in the beginning of another word or word-root. If it is put before a word or word-root, it is pre-fix, and if it is put after a word or word-root, it is suffix. I hope you understood. Still, for any other query, you are welcome to ask.