Swear words are an interesting aspect of a language, and one that learners come across surprisingly quickly. They are sometimes among the first words that you learn! It is important to be familiar with what they mean, so that you will understand when native speakers/native materials use them. However, you should be VERY careful when using them yourself. Some people say that they swear more in their second language because the words are less powerful or "don't mean anything" to them. This is not an acceptable excuse. If you can't associate a meaning with a word, you are going to have problems learning a language. That being said, there may be occasions when it is ok to swear. This evidently depends on the situation you are in and what level of formality you are using.