Public libraries make a lot of their information available online, so it's easy to reserve a book, access catalogues and search other libraries, without leaving your computer.
However, there are some services that public libraries can only provide onsite. At your local library you can browse the shelves, borrow several items at a time, and get help from the librarians. You can find your nearest public library by going to your local council website.
Reference librarians who you'll meet in libraries are experts at finding information, and will usually go out of their way to help you. They've probably searched for information on your topic before, so they will know how and where to find the best resources, fast.
They can also help you to search and use collections, catalogues and databases. If you know how to access different types of services in libraries, you'll get better resources and be a more efficient researcher.