It does a few things. If you are reading (top to bottom) the wheel is really useful. It scrolls in chunks tho. A touch pad is more accurate but I always attach

It does a few things. If you are reading (top to bottom) the wheel is really useful. It scrolls in chunks tho. A touch pad is more accurate but I always attach a mouse to my laptops. Not sure why but it feels less convenient than the scroll wheel. If you need to travel slightly further dragging the middle mouse "button" is great. I have no idea how to do that with a touch pad but one can also use page up and page down (or [shift+]space when available) If pages or documents are really long it isn't fast enough. I might roughly know where the thing I'm looking for is. Holding down the mouse button on that offset. Is faster. The scrollbar does both extremely fast and fine scrolling. I rarely start reading a page of code from the top. The larger sections are usually the most relevant. Here I hold the scroll bar and move it up and down quickly and accurately while reading. But the real trick is that it doesn't affect the cursor position. You can scroll then continue typing and it will jump to the cursor. [say] inline ccs, I'm typing some html but need to lookup what some class name was called. I can scroll to it, read and continue typing. Same for the name of functions and variables defined elsewhere in the same file. Or [say] I don't recall how to write someones name eventho I've already used it in the same article.