If there is a direct train, it is usually the fastest way to travel from A to B in Britain.
A stopping train stops at a lot of smaller stations between main stations. An express (train) provides a faster service to your destination, and avoids the problem of traffic jams on the bus services.
For rail travel, you might need a single or a return ticket. Many people buy a travel card, which allows them to travel on any bus or train in a specific area for a period of time for less money. A bus pass lets you do the same for bus routes. You can buy rail tickets online, from a ticket machine or at the ticket office I booking office in the station.
If you get a train or bus In time, you catch it. If you are late, you may miss it. You may need to change trains or buses.