public class WrapperOpp {
    
    
    //Our collection of the class/wrapper objects wrapAccount 
    public List<wrapAccount> wrapAccountList {get; set;}
    public List<Opportunity> selectedOpps{get;set;}
    
    public WrapperOpp(){
        if(wrapAccountList == null) {
            wrapAccountList = new List<wrapAccount>();
            for(Account a: [select Id, Name,BillingState, Website, Phone from Account limit 10]) {
                // As each Account is processed we create a new wrapAccount object and add it to the wrapAccountList
                wrapAccountList.add(new wrapAccount(a));
            }
        }
    }
    
    public void processSelected() {
        selectedOpps = new List<Opportunity>();
        Set<Id> accIds = new Set<Id>() ; 
        for(wrapAccount wrapAccountObj : wrapAccountList) {
            if(wrapAccountObj.selected == true) {
                accIds.add(wrapAccountObj.acc.Id);
            }
        }
        System.debug('acc'+accIds);
        System.debug('asdasd'+[Select Id , Name , Amount,CloseDate from Opportunity where  AccountId IN :accIds ]);
        selectedOpps.addAll([Select Id , Name , Amount,CloseDate from Opportunity where  AccountId IN :accIds ]);
    }
    
    
    // This is our wrapper/container class. A container class is a class, a data structure, or an abstract data type whose instances are collections of other objects. In this example a wrapper class contains both the standard salesforce object Account and a Boolean value
    public class wrapAccount {
        public Account acc {get; set;}
        public Boolean selected {get; set;}
        
        //This is the contructor method. When we create a new wrapAccount object we pass a Account that is set to the acc property. We also set the selected value to false
        public wrapAccount(Account a) {
            acc = a;
            selected = false;
        }
    }
    
    
}

<apex:page controller="WrapperOpp" >
    <script type="text/javascript">
    function selectAllCheckboxes(obj,receivedInputID){
        var inputCheckBox = document.getElementsByTagName("input");                  
        for(var i=0; i<inputCheckBox.length; i++){          
            if(inputCheckBox[i].id.indexOf(receivedInputID)!=-1){                                     
                inputCheckBox[i].checked = obj.checked;
            }
        }
    }
    </script>
    <apex:form >
        <apex:pageBlock >
            <apex:pageBlockButtons >
                <apex:commandButton value="Show Selected Opportunities" action="{!processSelected}" rerender="table2"/>
            </apex:pageBlockButtons>
            
            <apex:pageblockSection title="All Accounts" collapsible="false" columns="2">
                
                <apex:pageBlockTable value="{!wrapAccountList}" var="accWrap" id="table" title="All Accounts">
                    <apex:column >
                        <apex:facet name="header">
                            <apex:inputCheckbox onclick="selectAllCheckboxes(this,'inputId')"/>
                        </apex:facet>
                        <apex:inputCheckbox value="{!accWrap.selected}" id="inputId"/>
                    </apex:column>
                    <apex:column value="{!accWrap.acc.Name}" />
                    <apex:column value="{!accWrap.acc.BillingState}" />
                    <apex:column value="{!accWrap.acc.Phone}" />
                </apex:pageBlockTable>          
                
                <apex:pageBlockTable value="{!selectedOpps}" var="c" id="table2" title="Selected Opps">
                    <apex:column value="{!c.Name}" headerValue=" Name"/>
                    <apex:column value="{!c.Amount}" headerValue="Amount"/>
                    <apex:column value="{!c.CloseDate}" headerValue="Close Date"/>
                </apex:pageBlockTable>
                
            </apex:pageblockSection>
        </apex:pageBlock>
    </apex:form>
</apex:page>