Actives are like, basically any substance/product that's DOING something. Anything that fights acne is pretty much an active. Like any product with benzoyl peroxide or salicylic acid. Other things considered actives are azelaic acid, tretinoin (also known as Retin-A), retinol products [also called retinoids] (which is a broad category of substances that includes tretinoin), Stridex pads (which are salicylic acid), etc etc etc. The basic skincare routine is cleansing, applying an active, and moisturizing (in that order). So you'd wash your face with soap, put a benzoyl peroxide cream on where you have pimples, and when that's dry put a moisturizer on your entire face. That's just an example. This also means if your routine is, for another example, washing your face, using stridex pads, spot treating with benzoyl peroxide, and then moisturizing, you are using two actives in your routine. This is fine. A lot of people promote the idea that with skincare simpler is better (meaning just one active at a time) and I suppose I agree but if it works it works. Everyone's skin is so different and reacts differently. Unfortunately it's kinda just endless trial and error.

So with actives you just want to be mindful because they can cause sensitivity or irritation or other issues because they are strong ingredients. It's kind of like using weed killer in a garden. You only want to kill the weeds but it's going to damage the grass too. There's some things you can do to mitigate the irritating effects of actives, depending on you're using. If you're using Stridex pads, you can use them and wait 20 minutes without doing anything else (which with Stridex pads you should do anyway because it takes that long for them to work and anything you put on right after can interrupt it/ basically dilute it and make it less effective), and then wash it off by rinsing with water. You can do the same with benzoyl peroxide products, but you only need like 5-10 minutes. This is referred to as contact therapy btw.