cannot understand ogive diagram

i dont understand the figure .In my book After the basic definition of cumulative frequency curve the diagram is given ,no more details regarding.The curve which is starting from origin enough to grasp the information isn't it?.Then why there are two curves named as less than and more then.Thank you in advance

You can find lessons online which explain this topic. You could start here, but there are loads of others. Try searching for "less than and more than ogive graph" (without the quote marks).

Thank sire,Got it