What  you  mean by  simple present  and  simple past

The simple present or present simple 

is one of the verb forms associated with the present tense in modern English. It is commonly referred to as a tense, although it also encodes certain information about aspect in addition to present time.

It is called "simple" because its basic form consists of a single word (like write or writes), in contrast with other present tense forms such as thepresent progressive (is writing) and present perfect (has written). For nearly all English verbs the simple present is identical to the base form (dictionary form) of the verb, except when the subject is third-person singular, in which case the ending -(e)s is added. There are a few verbs with irregular forms, the most notable being the copula be, which has the simple present forms am, is and are.

The simple past or past simple

sometimes called the preterite, is the basic form of the past tense in Modern English. It is used principally to describe events in the past, although it also has some other uses. Regular English verbs form the simple past in -ed; however there are a few hundred irregular verbs with different forms.

The term "simple" is used to distinguish the syntactical construction whose basic form uses the plain past tense alone, from other past tense constructions which use auxiliaries in combination with participles, such as the past perfect and past progressive.