A suffix is a word part that can be attached to the end of a base/root word to form a new word. It has its own definition but can not stand-alone.
Additionally, unlike a prefix, a suffix changes the part of speech and sometimes the meaning of the base/root word to which it is added. Analyzing the base/root word and the suffix together create one new definition for a word. For example, the word reporter.
report + er
A report is a detailed document of a factual matter. The suffix '-er' means 'one who, a person associated with'. Thus, the word reporter means 'one who gives detailed information of a factual matter.'
Sometimes a word will contain both a prefix and a suffix. For example, counterclockwise.
counter + clock + wise
Counter- is a prefix meaning 'contrary/opposite.' Clock is a device indicating time by means of hands moving on a dial. -Wise is a suffix meaning 'showing how.' Thus, counterclockwise means 'showing the opposite direction of the hands moving on a clock.'
There are two kinds of suffixes: inflectional and derivational.