Confused on how many albums Beatles albums there are

Okay so I’ve become addicted to the Beatles after this summer after hearing one of their songs on the 60s Spotify playlist. I believe it was my guitar gently weeps. I’ve now been listening and learning about everything Beatles for the past half a year nonstop. Still I’m confused on what makes Beatles albums gain the title of a “album.” According to what I’ve read there’s 13 official Beatles albums but then I see albums that I’ve never heard of that were released between 1963-1970 like “introducing.... The Beatles” and for some reason that doesn’t count as one of the 13. Why is that? I need someone to educate me better lol.