Cracks in the external or internal brick work of a house can be a major problem and can cost you a lot of money to fix if you need to have a wall underpinned. There are many different types of cracks in walls, some are major that you will need a structural engineer to take a look at and some are minor which are due to settlement of the house that doesn't need any rectification but needs to be monitored. A building inspector will be able to point theses cracks out and advise you on what works need to be done.
Minor step cracks
When you have a building inspection done to your home the building inspector will look where the cracks are, how long the cracks are, how wide the cracks are and what direction the cracks are traveling.
Most brick veneer homes before the 1990s were not fitted with articulation joints to allow for expansion and contraction and subsequently step cracking in mortar perpends up to 4mm occurs which is common and to be expected.
If crack sizes exceed 4mm this can be caused by foundation movement. Moisture expanding soil causing heaving or in drier months soil contracts without the presence of moisture.
Major cracks to the brickwork
If still unsure I recommend consulting with a building inspector to identify if cracks are serious and require further investigation.