Prefixes generally change the meaning of a word, and suffixes change its part of speech (whether it is a noun, a verb, an adjective, or an adverb).

Prefix

By definition, prefixes are a group of letters that are added to the beginning of a word to change its meaning and make a new word. They have different functions:

“un“ as in “untidy” = NOT tidy
“re” as in “reproduce” = produce AGAIN
“mis” as in “misunderstand” understand WRONGLY 

Suffix

A letter or letters added to the end of a word to form a new word. Like prefixes, suffixes also have a variety of functions:

“less“ as in “sleepless” = NOT having enough sleep
“ly“ as in “consciously” = the ADVERB of conscious

Root word

The basic part of a word which shows its main meaning, to which other parts (prefixes and suffixes) can be added:

“bio“ as in “biology” = the study of LIVING CREATURES
“chrono“ as in “chronometer” = a tool for measuring TIME