Noun suffixes append to the end of words to change to meaning of a noun to something with a different, but related meaning. Examples of this in English would be adding ‘ness’ to the word ‘happy’ to get ‘happiness’. The thing being modified doesn’t have to be a noun (in the example earlier ‘happy’ is an adjective, not a noun) but the end result is definitely a noun.
Similar to appending a bunch of letters in English, in Cantonese this is done by appending an extra character to the word in question and you would get a new, related noun from the original word. An example of this would be:
科學 +家 → 科學家
Science + person → scientist
For GCSE Chinese the syllabus had explicitly mentioned five of these suffixes we need to learn how to use: