When you write an essay, you are creating an original work and when you use the works of others to form an opinion and/or assert a claim, it is essential to the integrity of your work to credit your sources. This is called a citation and you will find resources below that explain this in greater depth. When you use the work of others without their permission, it is stealing, or plagiarism. If you steal you are a thief and if you plagiarize you are a cheat. Understanding the significance of plagiarism is critical in this digital age when it has become so easy to copy and paste, but just as it is now easier to cheat...it is also easier to cite...you've got this!
Citation Machine is a free online tool for creating citations in multiple formats including MLA and APA.