That would be fairly high volume.
And that would be the overload part. Good on ya.
Where did you read the article, online or in a magazine? It was probably (hopefully) explained there.
Generally speaking, volume training is doing lots of work. A bunch of sets and/or reps. 10x10 (10 sets of 10 reps), 15x4, and 2x25 would be examples of high volume workouts.
Overload training is doing hard work. Lifting a weight that actually challenges you, as opposed to something you can easily manhandle. Lifting more next time than you did this time, would be overload. So would lifting close to a rep-max (whatever you can handle for a given rep range, and no more, sometimes nearing muscular failure.)
Overload is important for strength gains, volume is important for hypertrophy (muscle gains), and both are important to manipulate for maximum size and strength.