we elected him chairmam
主语we
谓语elected him chairmam
elected为动词过去式时态
we have elected him chairman
have elected为动词现在完成时时态。
谓语have elected him chairman
主语:这个句子所叙述的对象。
谓语:对主语加以说明的部分。
建议题主可以去看看哔哩哔哩上可汗语法看看,有帮助的