What is d-flex and col-sm-5 in Bootstrap

Hi

In below code what does this 2 lines means

<div class="col-sm-5 col-xl-5">
<div class="d-sm-flex flex-sm-wrap mb-3 mt-1">

<div class="col-sm-5 col-xl-5">
    <div class="card">
        <div class="card-body border-top-0">
            <div class="d-sm-flex flex-sm-wrap mb-3 mt-1">
                <%--  <div class="font-weight-semibold">Coordinator:</div>--%>
                <div class="ml-sm-auto mt-2 mt-sm-0">
                    <asp:Literal ID="ltrlName" runat="server"></asp:Literal>
                </div>
                <div class="ml-sm-auto mt-2 mt-sm-0">
                    <div class="font-weight-semibold">CurrentStatus :</div>
                    <div class="ml-sm-auto mt-2 mt-sm-0">
                        <asp:Literal ID="Literal1" runat="server"></asp:Literal>
                    </div>
                </div>
            </div>

Thanks