I've found a lot of queries about security of Knox and thus, Secure folder, comparison with other brands like Apple and Google security features and hardware-based encryptions. I'll try to brief you about Samsung Knox and it won't take you more than 3 mins to read.
Samsung KNOX runs on ARM's TrustZone while Apple relies on Secure Enclave.
Both have an isolated co-processor that is built on the same SoC and have different area of memory.
Let's see how hardware based encryption works and protects you:
Be it Secure Enclave from Apple, TrustZone from Samsung or even Titan M from Google, be assured that all of them works on advanced encryption algorithms like 256-bit AES. While the normal use cases of these hardwared backed chips are to store PINs, biometric information or payment data, we have an additional benefit of an isolated system with Samsung Knox's Secure Folder. TrustZone uses a secure area of the main processor to run critical software. Security keys can be stored here. Samsung’s KNOX security software runs in the ARM TrustZone area, so it’s isolated from the rest of the system. Samsung Pay also uses ARM TrustZone to handle payment card information securely. Knox has even garnered the approval of US Government, and is now allowing Samsung Galaxy phones to be used in government offices - a privilege long-held by Blackberry. This makes Samsung KNOX the most successful among all of the competitors.