The following are common methods you will want to call in your front end templates:
craft.navigation.nodes(nodeQuery)#See Node Queries
craft.navigation.render(nodeQuery, options)#See Rendering Nodes
craft.navigation.breadcrumbs()#See Breadcrumbs
craft.navigation.getActiveNode(nodeQuery, includeChildren)#See Rendering Nodes
craft.navigation.tree(nodeQuery)#Returns a full tree structure of nodes as a nested array.
craft.navigation.getNavById(id)#Returns the navigation for the provided id.
craft.navigation.getNavByHandle(handle)#Returns the navigation for the provided handle.