Marklin has always used track sections since they began and since it is AC and not DC, it is a 3-rail system.
Comparison of Marklin track:
Left is K-track, center is C-track and right is the old-school, no longer produced, all metal M-track.
There is flex track today in lengths of 3 feet and is for DC systems. The flex track can be bent to make curves and keep its geometry. I am unaware of a 3-rail flex track that an HO scale Marklin can run on.