Hi RitzyCat. In terms of your original question, computational biology involves the development and application of data-analytical and theoretical methods, mathematical modelling and computational simulation techniques to the study of biological, behavioural and social systems, and would include the foundations of computer science, applied math, biochemistry, molecular biology, genetics, biophysics, etc. It's similar to bioinformatics, which involves the use of computers to store and process data (in fact, I would say that bioinformatics is a subset of computational biology).
Biostatistics is a branch of statistics that is specifically applied to problems in biology and medicine (e.g. the design and analysis of clinical trials, the analysis of pre-clinical data, statistical analysis of genomics, analysis of epidemiological data, etc.)
From what I understand, you can work in computational biology or bioinformatics with a background in computer science, computer engineering, or applied math. Depending on what you do, it could involve anyone with just a BS to a PhD. As for biostatistics, one typically needs to complete at least a MS in either statistics or biostatistics to work in that field
Note: I'm a biostatistician working in the industry for over 10 years and I have a MS in statistics.