There're more detailed explantation of bioinformatics in the Internet if you have more interests in it. Simply speaking, with the rapid development of biology, the data produced by various kinds of experiments becomes more and more exponentially. In order to tackle the data, here comes the interdiscipline - bioinformatics. Some one may say that the bioinformaticians are just working for the experimenters. Of course you can think like that. After the experimenters produced the data, the bioinformatics take the job to analyze. However, if it's the bioinformaticians' idea to create an assumption and ask the experimenters to realize it. Can we say that the bioinformatics employed the experiments? Whatever, I think the man who offered the hypothesis is the key.
Talking so much about the field of bioinformatics, let's have a look how is our biology status so far. If we can count everything about 'biology' from primary school, in junior school, in high school and in university, I have been 'studying' biology for about 20 years. It sounds experienced, but for the researchers who really worked for 20 years after graduate, it's just a piece of cake. As a PhD candidate who didn't get the degree yet, I can only take a look at the small part in the ocean of biology which I knew.