So are there no sessions with pre-set trains moving about where you can just pick a loco and do some missions? Like cargos with their destinations that you can pick and deliver.
You can create your own, or you can take someone else's session and modify it for your own. You can even add in your own consists on the fly. You can also take over an AI-driven train and do what you want with it.
I for example like shunting and switching industries. On two routes I run extensively there are some fairly big yards with engine facilities and a passing mainline. On my very dense and busy Gloucester Terminal Electric route, I have trams busily going about their driving schedules, stopping at various stations, and repeatedly following a looped line. This route also has a switching line associated with it that serves various industries along the docks and some other line-side industries as well as a big quarry operation. This busy line is connected to a mainline that runs east and west to and from Boston and Rockport upon which I run passenger and freight trains at 17 minute schedules both ways.
I will make up a train in the yard for delivery to various industries or sometimes take goods from these industries and place them on the interchange track for the mainline. To get an AI train to pick up the freight, I will take over that train, take the engines off and direct the AI to go visit the engine facilities. While they're "being serviced", I will switch in and out any wagons I want to forward on to the outside world. Once I'm done switching, I'll move my switcher to a spur in the yard, and direct the AI to couple on to the train and continue on their journey in whatever direction they were heading.
As far as actual passenger schedules go, no there are none which is what the others were saying.
I recommend editing a session to see how it's done. Some of these can be quit complex, while others are quite simple. There's also a good wiki article, link above on how to build a driver schedule using simple Drive-To or Navigate-To destinations (industry or station) plus Navigate via and Drive via track marks.
To be honest, I highly recommend keeping things as simple as possible in the beginning. This is the best way to learn the ropes and once you've mastered that, you can try other more complex things.