How do you create graphs in web apps?

I know this question is probably very basic, but I am a beginner so I hope it is justified. I tried searching but could not really find anything basic on the topic. So... if I have a web app with users that are generating certain numbers over time and I want to create a pie chart and scatter plot of this data how would I do this? I thought of making a bunch of jpgs with different charts at different values but that would be ridiculous so I am assuming there is an easier way to do this. Is this true?