Basically, ETFs are entities that manage money for you

They are pretty much the same as personal money managers in regard to what they do (i.e. manage your money), but they are more regulated in respect to which markets they are allowed to trade on, i.e. in which assets and financial instruments they can invest the money of their clients. People are using these if they can't trade on their own since they might not have enough expertise or just be busy doing something else. Consequently, Bitcoin ETFs are the money management entities which would be investing in Bitcoin and Bitcoin derivatives (such as futures and options)