Styles are a collection of predefined formatting options that can be applied to text, paragraphs, or documents.
Styles are available within the home tab of Microsoft Word under styles
Select some text and notice, as you hover over each 'Style' available in the top tool bar it will display how that style would affect your text if applied. Notice also that there is a scroll bar to the right of the styles. click on this to see the extended list of options. If you have put together a particular style that you wish to keep (perhaps a combination of font size, type, colour etc.), select this and "save selection as new quick style"