Learned and Learnt mean the same, both are the past participle and the past simple of the verb Learn. The difference between these two words is that Learned is used in the american english and Learnt is used in the british english.
There are more examples:
burned, burnt
dreamed, dreamt
kneeled, knelt
leaned, leant
leaped, leapt
spelled, spelt
spilled, spilt
spoiled, spoilt
That's it and good luck learning english :D