There are different types of primary and secondary, but this time, I will focus on primary and secondary sources. When you say primary source, this means that the person that you are getting the information from is someone who has encountered the actual situation.
For example, a victim of theft may recall the details that occurred based on his own experience. He is the primary source because he experienced the situation. When you say secondary source, this means that the person has received the information from someone else but cannot be considered as the bearer of first-hand information. Take note that secondary sources can cite details from primary sources.