Why does Spanish have two words for this single meaning? What’s the difference between them?

Every language has synonyms and near-synonyms. English has plenty of them. You’ll get used to the slight differences in meaning and usage by getting lots of input, as you did for your first language. By hearing them in different contexts, you’ll acquire them as two completely different concepts without any need to compare them or to connect them to each other in any way. That’s how you’ll manage to learn their nuances well and use each word naturally without having to think about which one to use every time you need to use one. Do not try to learn their differences explicitly. That's the worst that you can do, since it will connect the words to each other in your head unnecessarily, and you will be actively causing the confusion you were trying to avoid. We also answer this question in our video FAQ (with English subtitles):