Normalization is one of the basic concepts. It means that two things do not influence on each other.
In databases specifically means that two (or more) tables do not contain the same data, i.e. do not have any redundancy.
On the first sight that is really good because your chances to make some synchronization problems are close to zero, you always knows where your data is, etc. But, probably, your number of tables will grow and you will have problems to cross the data and to get some summary results.
So, at the end you will finish with database design that is not pure normalized, with some redundancy (it will be in some of the possible levels of normalization).
