The HR department should be your first port of call if you are experiencing any issues within your job. They can also be an important contact if you are looking for a new job or have just been offered a new position. HR can give you lots of information about a position that you might not be able to get from anyone else.
If you are experiencing any issues at all, make sure HR are aware. These could be personal issues or they may be problems directly linked to your job, such as a difficult manager or struggles with your workload. An HR employee will be able to give you support and advice on the issue and they will not be able to tell anyone about it without your permission. They will have a good knowledge of workplace rules and regulations, as well as your specific company, so they are in a good position to advise you.