PCB bridged solder joint is formed by melting two solder joints together, forming an unintended connection between the two. The spacing between connections is quite tight, so you can easily bridge across two terminal connections. You can check by testing for shorts between each connection or use a magnifying glass to visually examine the connections.
You can avoid this only by using enough solder to make a good joint, because solder bridges often happen between joints with too much solder to begin with. If you have to tackle the solder bridge, it is not difficult. Sometimes the excess solder can be drawn off by dragging the tip of a hot iron between the two solder joints. If there is too much solder, a solder sucker or solder wick can help get rid of the excess.