一般现在时表示经常性习惯性发生的动作，常与sometimes ,often ,usually , every ...等时间状语连用，主语是第三人称单数时，谓语动词要加s 或es, be动词用is
如
He is a student.
He goes to school on foot.
一般过去时表示过去某个时间发生或存在的动作或状语，常与yesterday (morning ,afternoon, evening ),... ago ,last night /week 等时间状语连用
如：
He was at home yesterday.
He went to the park last Sunday .