For someone that doesn't understand twitter, what does that mean?

Twitter allows users (typically companies) to "promote" tweets, causing them to be seen by users who are not following the account, and hence would not typically see the tweet.

When a user promotes a tweet, they are given the option to hide it, so that it won't show up to users who are following the account directly, or who are looking at the account's profile. This is so that (for example) a company that posts a dozen different variants of an advertisement for different markets won't have all twelve of those show up on their profile page, or on the timeline of any user who's following them.

Apple, for whatever reason, seems to set the "hide this" option for every tweet they post and promote. Why? Beats me.

I think they do it for brand reasons. Having an empty Twitter page makes it seem like they're "above it all".

It means they use paid tweets (ads) to ‘tweet’.