>>107183
Encoding, not encryption, but I'm splitting hairs.
>>107168
Base64 encoding is a way of changing how text is represented from one form to another, generally to avoid characters that are "illegal" in a representation. Think of it like having a username field where "#" isn't a valid character. B64 started to get used in these parts because sites were automatically scraping for the content with uploads and sending takedown requests. It also meant that a website wouldn't get the referrer info from a clickthrough (prior to when it was popular to automatically strip that).