Simple Present

Things that happen every day.

Example: He usually goes for a walk every afternoon.

Simple Past

Something that happened in the past.

Example: I ate a sandwich yesterday.

Something that began in the past and continuous to the present.

Example: I have been in Valencia for four months.

Something that happened before something else.

Example: I travelled through france before arriving in Valencia.

Something that has not happened yet.

Example: I will go to the bathroom.

will + [root form of verb]

or:

[am/is/are] + going to + [root form of verb]

negative

will not + [root form of verb]

or:

[am/is/are] + not going to + [root form of verb]

Something that will have happened before a certain point in time.

You will have cleaned your room by tomorrow.

will + have + [past participle]