I do not know how they are different when they are used as a grading system ? Can I say a pointing system or a marking system?
The American Heritage Dictionary of the English Language, Fourth Edition, gives one definition of the verb mark as "to evaluate (academic work) according to a scale of letters or numbers; grade." In this sense a grading system and a marking system are equivalent. Similarly, in the United States you will hear regional variations where a grading period in one area is the same as a marking period elsewhere.
But the verb point is not synonymous with the verb grade. So a pointing system is not the same as a grading system.
However, the noun point is synonymous with the noun grade. From the same dictionary, one of the definitions of the noun point is "a numerical unit of academic achievement equal to a letter grade." Similarly, the noun mark is defined as "a number, letter, or symbol used to indicate various grades of academic achievement."
Therefore, grade, mark, and point are synonyms when used as nouns. But only grade and mark are synonyms when used as verbs.
In the example I'm giving, I'm using primary(elementary for those who don't speak real English) school test system.
A mark determines whether a question is right or wrong.
A point is awarded if a question is correct.
The combined point score will give you your grade.
The term "grading system" makes the most sense to me.
"Grade" is used when determining the quality of something, for example, high-grade diamonds, or low-grade pearls, etc.
"Points" are used when it is a point system. Point systems can be seen in things like the English Soccer League, where each game won earns you a certain number of points. The number of points gives you a grade. For example, if Manchester United has 67 points, and it has more points than anyone else, then it has a grade of number 1. If Chelsea had 66 points, then because Manchester United has 67 points, Chelsea won't be number one, but number 2. (Grading and giving points are closely associated).
Marks, are the same as points, just a different word, and sometimes used in different places. For example, we use "marks" for the result of an exam, not point.
Edit: To make myself clearer, :
Points are a fine distinction of goodness or badness. On an exam, they typically range from 1 to 100.
Grades refer to RANGES of points. In American colleges, typically 91-100 points represent a grade of "A," 81-90 represent a grade of "B" etc. Usually, there is no distinction in grade between, say, 94 and 95 points, although some systems break down the ranges further with pluses and minuses: e.g. 98-100= A+, 94-97=A, 91-93 = A-.
"Marks" is a "catchall" term that could refer to either points or grades, but in either case, refers to methods of evaluation.