What is the difference between a railway track pin and a track nail?
There are several types of track pins and nails available to secure model railway track to a baseboard. Generally, a track nail is thick and strong (but by default is more visible) while a track pin is thinner and less obvious but is also weaker and more fiddly to install.
Which you use is a personal preference but on balance, track nails have more advantages as they are the correct size to fit the pre-drilled holes in 00 gauge set track, they are also stronger so do a better job of embedding themselves into harder baseboards and are less likely to bend if you're using a hammer to install them.
Track pins on the other hand, are often used by modellers that desire the most realism. In this case, though, it is most likely the modeller will only be using pins to lightly hold their track in place while glue is used to provide a permanent fix and the pins will be removed once the glue has dried.
If you are still pondering whether you should use track pins or track nails, ask yourself if you are a meticulous modeller with lots of patience. If so you may well benefit from the discrete appearance and smaller holes made by the thinner (and more bendy) track pins, however, if you would like to install your track and have hair left at the end of it, maybe go for the nails!