I am a Pole living in the United States and I am currently spending my summer back home in Poland. I took a train trip to see a Bon Jovi concert in Gdańsk, and as I am based in Lublin, which is very close to the Ukrainian border in the east, I took a train. I decided to take a lot of pictures and just try to help you get a feel of taking a train in this country. 
The first thing I'll explain is that in Poland, all of the railways that are used by passenger trains are state-owned and the carrier is also state-owned as well. The Regional railways operator is owned by the local governments, but it's still public, obviously, while the PKP Intercity corporation is a state corportation (owned partially by Deutsche Bahn as well).
There are couple of "classes" of trains with PKP Intercity. TLK is a standard intercity train, which means Twoje Linie Kolejowe (Your Rail Lines). There is also a special class, Express Inter City (EIC) which is an express train. One must note, however, that currently, the maximum speed limit in Poland is 100 mph (this will soon change with the arrival of Pendolino trains).
So the trip I took I could have taken in one train, the one I started out with, but instead, I decided to take a 3,5 hour break in Warsaw for two reasons. One is that I was able to meet my friend there, but one more important reason is that for the price of a standard TLK train, I travelled in an Express Intercity class train, that was degraded for 2 years to a TLK price, due to construction etc. However, the standard remained the same. One big example is that compartments are for 8 people in a regular 2nd class car of the TLK trains while EIC has 6 and has an on-board restaurant, AIR conditioning in cars etc.
So I was scheduled to depart at 10:10 AM by TLK Wieniawski going to Bydgoszcz and some cars to Gdynia, but I would get off in Warsaw at 12:45 and get on TLK Kaszub at 4:20 PM. I would get off in Gdańsk at 9:25 PM.
So here is my ticket:
and an additional seating reservation (all PKP Intercity trains have assigned seats)
Unfortunately, I had to take a bus to the train station [;)]
The main train station building in Lublin looks like this
I entered by the side entrance, which is an underground pass directly to the platforms, bypassing the station building. Upon getting on the first platform, I saw an old style EN57 regional train to the Lublin airport.
But I soon found out that my train would depart from platform 2, so I headed to an underground pass to platform 2.