There isn't a difference. 'Start' can be used with either a gerund or an infinitive. There may be a slight difference in some cases, depending on what you know about the context, but the distinction is very subtle. "I started learning English two years ago" and "I started to learn English two years ago" have the same meaning. NB Don't believe everything you see on the internet - there is a lot of misleading and incorrect information out there. For example, your explanation in your comment above (En internet he leido que cuando usas "to learn" significa que no lo has planeado y con "learning" lo has planeado.) is complete rubbish. I can only guess that somebody was confusing this with statements about the future.

to start to learn something significa que acabas de empezar a aprender algo y to start learning something significa que ya ha emezado a aprender algo o sea estás en ese process de aprender algo