求大神，这个style="display:none;"该怎么解读？

Question

<script language="javascript">
function pysjzx_change(){
var leaseObj = document.all.id_lease;
var saleObj = document.all.id_sale;
var hhObj = document.all.id_hh;
var pysjzx_type = document.pysjzxform.pysjzx_type.value;
if (pysjzx_type=="sale"){saleObj.style.display = "block";leaseObj.style.display = "none";}
if (pysjzx_type=="buy"){saleObj.style.display = "block";leaseObj.style.display = "none";}
if (pysjzx_type=="lease"){leaseObj.style.display = "block";saleObj.style.display = "none";}
if (pysjzx_type=="hire"){leaseObj.style.display = "block";saleObj.style.display = "none";}
if (pysjzx_type=="cotenancy"){hhObj.style.display = "block";saleObj.style.display = "none";}
}

请高手详细解答一下这段代码是什么意思