vocabulary - discerning between the usage of raise and rise?

I am wondering if there is any difference between the bold parts?

these are extracted from Longman:

rise: increase: to increase in number, amount, or value [= go up; ≠ fall]

raise: increase to increase an amount, number, or level [≠ lower]:

Answer

They do not always mean the same thing in different contexts. They are similar, yes, but they have different impacts on sentences. It takes a bit to figure out adequate usage but you'll get it sooner or later.

Your examples:

• "Sales rose by 20% over the Christmas period" = The amount of sales increased by 20% over Christmas


• "Many shops have raised their prices" = Many shops have increased the amount of their products, therefore increasing their prices

See, the examples you used have similar meanings but the word "raise" is commonly used in a context where it refers to an entity.

Watch my usage:

• 
  

  Upon asking him what he does for a living, the goat herder muttered "I raise livestock for my daily bread". (This usage focuses on the word raise referring to the growth or increase, yes, in size and not volume of an entity "livestock". It is not the same as any equivalent using the word "rise".

  
  
  


• 
  

  Watching the prices rise slowly was a nerve-wrecking experience for the stock broker. (This is focused on an increase in direct value in a quantitative sense). Not the same as an example of the word "raise"

  
  

I don't believe in dictionary definitions being the only way to use words in English but I would advise you to read the following links so you can understand a bit more of the usage and discern for yourself.