Homophones are words that are pronounced the same way but have different meanings. Sometimes they’re spelled identically and sometimes they aren’t. Types of homophones

Your/you’re
Your is a pronoun that shows possession:

• 
  I’ve never been to your house.
  

You’re is a contraction of the words you and are:

• 
  You’re invited to my birthday party next week.
  

More of the most common English homophones

• 
  by/buy
  
• 
  affect/effect
  
• 
  whether/weather/wether
  
• 
  principle/principal
  
• 
  brake/break
  
• 
  waist/waste
  
• 
  week/weak
  
• 
  complement/compliment
  
• 
  discreet/discrete
  
• 
  bail/bale
  
• 
  bear/bare
  
• 
  here/hear
  
• 
  illicit/elicit
  
• 
  sight/site/cite
  
• 
  led/lead
  
• 
  carrot/caret/carat
  
• 
  bark/bark
  
• 
  be/bee
  
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  whole/hole
  
• 
  seal/seal
  

Why do languages have homophones?
There are a few different reasons why languages have homophones. Some languages have significantly fewer phonetic syllables than others and this limited syllable set makes homophones almost inevitable. Chinese is one such family of languages, and with Chinese dialects’ emphasis on context, homophones play an important role in communication and understanding. 
In other languages, such as English, homophones largely stem from words’ pronunciations changing over time. All languages evolve as people migrate, mesh with new cultures, develop new technology and new needs, and integrate new languages with their own. Languages evolve into distinct regional dialects as well and sometimes, words that are homophones in one dialect aren’t homophones in another. One example of this in US English are the words “marry,” “merry,” and “Mary.” In some parts of the US, these three words sound the same and in others, they have distinct pronunciations. 
Many of today’s homophones didn’t start out as homophones. One example of English homophones that were initially pronounced differently is knight and night. The word “knight” was spelled “cniht” in Old English and it was related to the Dutch word “knecht,” both of which pronounce the letter “k” at the beginning of the word. “Night,” on the other hand, evolved from the Old English “neaht” and “niht.” Following the Norman Invasion and English’s shift away from its Germanic roots, the pronounced “k” sound began to drift away, leaving us with a silent letter at the beginning of the word “knight.” Other words, like “knot,” “knife,” and “knit,” followed a similar progression as English evolved from a strictly Germanic language to one with significant Latin influences.