It has following two methods :

1. generateUrl : This method is use to generate url for a given page reference. This method used   ‘page reference’  as parameter.
2. navigate : This method is used to navigate to specified page reference. This method used two parameters ‘page reference’ and ‘replace’.

#page reference : It is an object which have following properties.

• type : It defines api name of page, for example : for standard object page we use ‘standard__objectPage’ , for record page type we use ‘standard__recordPage’. It is required.
• attributes : It is also required. It defines the value for each attribute to generate pagereference, for example objectApiName, recordId, action.
• state : This property is optional. This property defines parameter of page url to be generated.

#replace : It is boolean value which indicates whether new page should replace the current page in navigation history. It is optional.

Note : To use this component we must implement “home:availableForDesktop” or “flexipage:availableForAllPageTypes” interface.

In this example we are going to generate a navigation link which navigate to standard account list page and a record view page.
#Component

<aura:component implements="flexipage:availableForAllPageTypes">
     <aura:attribute name="url" type="String"/>

     <aura:handler name="init" value="{! this }" action="{! c.setPagref }"/>
     <lightning:navigation aura:id="navLink"/>
     <div>
        <a href="{!v.url}" target="_blank"> Go to Account </a> <br/>
        <lightning:button label="Andy Young" title="Andy Young" onclick="{!c.goToRec}" variant="success"/>
     </div>
</aura:component>

#Controller

({
    setPagref : function(component, event, helper) {
        var navLink = component.find("navLink");

        var pageRef = {
            type: 'standard__objectPage',
            attributes: {
                actionName: 'list',
                objectApiName: 'Account',

            },
            state: {
                filterName: "MyAccounts"
            }
        };

        // Set the URL on the link or use the default if there's an error

        navLink.generateUrl(pageRef).then($A.getCallback(function(a) {
                component.set("v.url", a ? a : "#");
            }), $A.getCallback(function(error) {
                component.set("v.url", "#");
            }));
    },
    ge : function(component, event, helper) {
        var navLink = component.find("navLink");
        var pageRef = {
            type: 'standard__recordPage',
            attributes: {
                actionName: 'view',
                objectApiName: 'Contact',
                recordId : '0037FXXX51uq5QAA' // change record id. 
            },
        };
        navLink.navigate(pageRef, true);
    }
})

–> Component Output :

–> Url generated by “setPagref”function is : “/lightning/o/Account/list?filterName=MyAccounts ”

–> Navigation url in “goToRec” function is : “/lightning/r/Contact/0037F0000051uq5QAA/view”

That’s all about lighning:navigation in lightning component still if you have any further query, feel free to contact us, we will be happy to help you
https://wedgecommerce.com/contact-us/