bit flippers pretty much hit the nail on the head but if you're interested, here are a couple of other ways that haven't been mentioned so far
Holding down Z allows you to enable a magnifying glass zoom. You can then click and drag an area you want to zoom in (I find it helps when looking at a coupe of tracks clsoe up). Something similar is available in pro tools
By pressing U you can revert to the previous ZOOM
also by pressing "F" you can fit all your tracks to the vertical screen space
and Shift + "F" will allow you to fit the entire project to the vertical and horizontal parameters.
the last 2 are a bit depenedent on the track count in as much as that if you have a high track count the tracks will be their smallest vertical size possible and scrolling may be needed to see everything. At this point, folders can become a a really big help navigating through your project