Let's focus on those last two. The most interesting two.
But we have to go back a step, first.

The skin's natural exfoliation process:
Our skin is naturally renewing itself, every month. This cycle involves the production of new cells at the innermost layer of the epidermis (basal), which then slowly migrate to the surface to replace old or dead cells.
The final phase of this cycle is called desquamation, a shedding, when your body decides to rid of the dead cells from the outermost layer of the epidermis (stratum corneum).

Several lifestyle and environmental factors can impair this process, which is why you start to see build-up on the skin in the form of dullness, clogged pores, dryness, and flakiness.
When your skin cells take longer to complete this 'turnover' it is often a result of increased stress, hormones, dehydration, or aging skin. Dictating when it's time to incorporate an exfoliant into your routine.
By gently removing this build-up you limit the resistance; products are able to sink deeper into the skin, so you can receive a more potent dose of active ingredients. This is particularly beneficial when using retinoids, vitamin c, or peptides. Your anti-aging or brightening treatments will see the best results with regular exfoliation.
A refiner shouldn't be the nice-to-have in your skincare routine. It's a hardworking product that prepares the skin for visible transformation. It's how you build a healthier and more responsive barrier.