How is this range update working?

general
1

Can anyone explain this range update function of segment tree? It’s faster from normal range update but I can’t understand how it is using lazy propagation.
The question was to increment all values from ind1 to ind2 by 1.

void update(int st,int en,int ind1,int ind2,int node)
{
    if(st>en)return;
    if((st>ind2)||(en<ind1))return;
    if((st==ind1)&&(en==ind2))
    {
        segNode[node]++;
        return;
    }
    int mid=(st+en)/2;
    if(ind2<=mid)update(st,mid,ind1,ind2,node*2);
    else if(ind1>mid)update(mid+1,en,ind1,ind2,(node*2)+1);
    else
    {
        update(st,mid,ind1,mid,node*2);
        update(mid+1,en,mid+1,ind2,(node*2)+1);
    }
    return;
}