[语法]句子+逗号+AND+句子和句子+逗号+句子有什么区别

[语法]句子+逗号+AND+句子和句子+逗号+句子有什么区别
There were fifty people in the village, the old included.= There were fifty people in the village, and the old were included.
It was fine, and we went out for a picnic=It being fine, we went out for a picnic.
这两句话意思相同。。为什么有的句子有And有的句子不用而时态变了呢？