AWS s3 file upload in express js: whats the difference between upload vs multipart upload

I am trying to upload a file to AWS s3 using express js,instead of putObject i am using upload http://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/S3.html#upload-property function

       var options ={
            partSize: 5242880, queueSize: 1
        };
        console.time('Uploadtime');
        s3.upload(params,options,function(err, data) {
            if (err) console.log(err, err.stack); // an error occurred
            else     {
                console.timeEnd('Uploadtime');
                console.log("uploaded",data);
                res.json({
                    'status':'Uploaded'
                });
            }           // successful response
        });

I think upload and multipart upload do the same thing(am i correct??) My question is do i need to use multi part upload or stay with upload method.

From the docs i can't get the similarities between upload and multipartupload

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