Normal delete just marks things as deleted, freeing up that space to be overwritten later, but the original data is still there until it is overwritten. Secure delete overwrites the data with random 1’s and 0’s, so it is actually gone and can’t be recovered. It’s the difference between throwing a physical document into the trash, but not taking the trash out, or instead putting the physical document through the shredder and then burning the shredded paper. In the first example anyone with access can reach into the trash can and read your document, and in the second example it’s unrecoverable.
Normal delete just marks things as deleted, freeing up that space to be overwritten later, but the original data is still there until it is overwritten. Secure delete overwrites the data with random 1’s and 0’s, so it is actually gone and can’t be recovered. It’s the difference between throwing a physical document into the trash, but not taking the trash out, or instead putting the physical document through the shredder and then burning the shredded paper. In the first example anyone with access can reach into the trash can and read your document, and in the second example it’s unrecoverable.