Sample Code:

Visualforce page1:

<apex:page controller="Sample">
<apex:form >
    <apex:pageBlock >
        <apex:pageBlockButtons >            
            <apex:commandButton value="Next Page" onclick="show();"/>
        </apex:pageBlockButtons>
    </apex:pageBlock>
</apex:form>
</apex:page>

Apex class:

public class Sample {
    public Sample() {
    
    }
    
    public PageReference next() {
        return Page.Sample1;
    }
}

Visualforce page2:

<apex:page >
This is the second page.
</apex:page>

Output: