There are over 55,000 programs posted on the web site. Download some you are interested in and try reading them to see how they work.
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All scratch programs are completely open source. You can download all the codes yourself.
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Bluey55,
Your best bet is to look at projects that interest you and figure out how they work. Stick to ones that work well and have a small number of sprites and scripts. The first one I downloaded was this one by MrShah:
http://scratch.mit.edu/projects/MrShah/29484
It is one sprite/one script, looks cool, and is easy to understand, as Kevin pointed out, there are a huge number of possible projects to look at.
You can study or experiment with the projects that you download to learn how they work. I usually download projects and open them directly in Scratch to have a look, then just close Scratch, but you can also save the project to your own computer if desired.
Hope this helps.
-MrEd
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