I haven't watched the movie in 25 years, but from memory the premise is that corporations use human brains as organic/wetware hard drives to transfer information because hardware-only storage has largely maxed out or would be too cumbersome for information smuggling.
In the movie, the base storage capacity of the human brain is said to be 80gb, though the protagonist is able to increase his storage capacity to 320gb by using a cybernetic implant and agreeing to dump a bunch of his childhood memories to make extra room.
This seemed like a ludicrous amount of data to 10 year old me. Our recently purchased top of the line 486 had a 400MB hard drive, so the amount of data stored in Keanu's head was nearly 3 orders of magnitude more.
Exponential growth is a hell of thing.