The difference between order by and group by in MySQL

The following is a detailed analysis of the difference between the order by and group by in MySQL, the need for friends can come to the reference

ORDER By is understood in English as the sort of row, and the default is ascending. The ordered by must be followed by a list of field names, which can be multiple field names.
GROUP By is understood in English as grouping. You must have an aggregate function to work with, and you need at least one group label field when you use it.
What is "aggregate function"?
like sum (), COUNT (), AVG (), etc. are "aggregate functions"
The purpose of using group by IS to subtotal data.