What’s the difference between timestamp, last_traded_at and last_fetch_at?

Example: 

https://api.coingecko.com/api/v3/exchanges/binance/tickers

• ticker.timestamp - refers to the last time that we call the exchange API to retrieve the price of a certain pair
• ticker.last_traded_at - refers to the last time that the price of a certain pair has changed.
  
  Therefore, both json.timestamp and json.last_traded_at are the same, returning the last time the price of a certain pair has changed. 

Meanwhile, json.last_fetch_at returns the timestamp of the last time we called the exchange API to retrieve the price.