Rail tickets Spain. Train travel in & to Barcelona
Rail train travel in Spain - Barcelona trains
In Barcelona and throughout Spain, RENFE are the main trainand rail company. RENFE has routes all across Spain and to all of the major cities such as Barcelona, 
Madrid, Valencia and Bilbao.
You can get to most places in Spain with this Spanish rail train system. Prices are reasonable and the frequency of trains is also not too bad.
Rail train travel coming via France
It might be that you are travelling into Spain via the southern area of France, i.e. by rail down to
Barcelona. SNCF are the main train and
rail travel 
company in France.
From cities such as Montpelier in France you can easily connect to Barcelona. Your best bet though is to phone SNCF or RENFE and get up-to-date details on rail travel connections to and from Barcelona and France.
Rail train travel coming via Portugal
Another possibility is that you are traveling from Portugal to your destination in Barcelona 
or elsewhere in Spain. In Portugal the rail system is CP Passageiros.
From my own personal experience, the trains are fairly reliable between most major cities and the cost of train and rail travel in Barcelona.
