Affiliate links have a special code in the URL. If you register from this link, some companies will give free credits to either both of us or just to me (depending on how a company set up their affiliation program - I always ask if they have some coupon codes that will give credits to both sides). Those credits can be used on their website (for a few months of free hosting, a cheaper domain, etc.) or redeemed for money (only for domains providers).
Affiliation program doesn't affect whether a company is recommended or not. You can read more about how I select companies/tools on the About & contact page.