Answer :

Plagiarism is Copying ideas or answers or anything from someone else. 
Like in a school project, Your teacher asked you to do a project about biodegradable things. Your friend decided to do About the orange peal, so you do the same and maybe add something. That's called Plagiarism.

Just don't copy others ideas, and you'll avoid it :)

Hope this Helps! :D
plagiarism is taking credit for someone's work. for ex. you have to write a report for Jupiter and you find one online, print it out, and put your name on the paper. you can avoid plagiarism by quoting what you took from the source you are using, make a citation page and insert foot notes.