:gutter='20'和:span到底代表啥区别？

 <el-row :gutter='20'>
      <el-col :span='6'><div class="gutter">132465</div></el-col>
      <el-col :span='6'><div class="gutter">132465</div></el-col>
      <el-col :span='6'><div class="gutter">132465</div></el-col>
      <el-col :span='6'><div class="gutter">132465</div></el-col>
      <el-col :span='6'><div class="gutter">132465</div></el-col>
    </el-row>

:span是每个元素所占此row比例，一行是24
:gutter是该row内元素之间的间隙，也就是col占6，gutter占6中的20px