First of all, welcome!
I'm going to make reference to "environments" in this post. An environment is a specific landscape with a flat area to build your track with a set of blocks (track pieces) that are unique to that landscape. The physics of the environment are bound to a single type of gameplay. You can use different 3D models and skins/liveries for your car, but they will all behave the same way and have the same speed, turning, etc... within that environment. This makes TrackMania an extremely fair and level playing field when it comes to driving against other players. It really comes down to your skill against theirs. There are no collisions with other cars, meaning no one can ruin your run, which is good, because many tracks are hard enough as it is without having someone crashing into you all the time. The term "Environments" is also now synonymous with the term "Titles" since each Environment is sold separately as its own standalone title within the ManiaPlanet universe.
Okay, on to your question... are there any players? It really depends when during the day you play.
At high volume times for players (usually in the evening for europeans) you can get 20 to 40 players on some top servers in TrackMania 2 Canyon. This was a title/environment released September 2011. So it's been out a while. Still, there are many people playing it.
The PMC (Planets Millions Cup) held once a month on 4 endurance tracks (8 to 12 minutes to drive from start to finish) sees anywhere from 80 to 180 players join in. I always try to participate in that. It's so much fun! It's on the third Thursday every month, and everyone is welcome, even if you just started playing.
There's also competitions held regularly for individuals and teams. There's different modes, Time Attack (its like time trial... where you go for the best time in a given timelimit), Rounds (where everyone drives together and tries to finish first... this is the mode PMC is played in), and other modes based on Rounds like Team mode.
The new environment announced yesterday, TrackMania 2 Valley, will no doubt bring a lot more people to the game, as well as bring back some who aren't so active right now. One thing is certain, I'm sure you'll see a big surge in activity. But none of us have played it yet, so we're not sure how much we'll like it.

We all have high hopes though I think.
The other new environment announced yesterday is TrackMania 2 Stadium. It's actually the same environment included in the free TrackMania Nations Forever released in 2008, and Nations Forever was itself an update to the free TrackMania Nations ESWC game released in 2006. It became very popular in eSports and was played by millions of people. It's what originally got me into TrackMania. When TrackMania Nations Forever was first released, it was not uncommon to see the first 10 or so servers have 100+ people on them all the time.
This update to bring the environment in Nations known as "Stadium" into ManiaPlanet (a multi-game platform for PC) will bring a lot of new players to the game (like yourself

), as well as bringing a lot of well seasoned players back to try out the new stuff. I'm certain that you're going to see multiplayer servers packed with players upon release, and probably during the beta as well.
There's a lot more history behind TrackMania, but I'll try to keep it simple for now. ^_^
I will mention that one of the highlights of this game is the track editor. It's extremely simple to use. There have been hundreds of thousands of tracks released by players. Some bad, some good, but always interesting.

Many track styles have developed. Technical ones, fullspeed, transitional, and even platformer type tracks where you jump from one place to another.
There are also many who play offline some or much of the time and upload their best replays to the track sharing site
Mania Exchange, myself included. Others play in LAN mode a lot with friends or even on private servers. The community is worldwide and as varied as people are.
Whether you go online for some competition, or race offline against someone else's ghost replay, the experience never gets old... at least for me.
Well, that sounded a little like an ad.
