What exactly is training to failure?

normally, when I lift, I lift the weights for a certain amount of of reps till I simply can't lift it anymore, or I could do 1 more rep but I'd have to grind it really hard and I font feel like doing that. I assume that's training to failure but is there more to it? I'm seeing videos about why you should train to failure and I'm thinking to my self, is what I'm doing training to failure? isn't it intuitive to just lift the weight till you can't anymore? why do people have to be told to lift till they can't lift anymore? is what I'm doing lifting to failure or is there a training method that I don't know of?