The word tense means time. There are three times (present, past and future) at which an action can take place.
A) Simple Present/Present Simple - everyday, sometimes, always, often, usually, never, etc.
i) something happens repeatedly
ii) how often
iii) things in general
iv) timetables
For example, I work, I don't cook, he goes, he doesn't go, she sings, etc.
B) Present Progressive/Present Continuous - now, at the moment, currently, etc.
i) something is happening at the same time or around it
ii) a fixed plan or time
For example, I am working, he is studying, Mei Mei is going, Mei Mei isn't going, etc.
C) Simple Past/Past Simple - yesterday, just now, long time ago, last week, etc.
i) action finished in the past
For example, I ate, he ran, Mei Mei went, Mei Mei didn't go, etc.
D) Past Progress/Past Continuous - while, when, etc.
i) action happened in the middle of another action
ii) action happened in the past that you do not know whether it was finished or not
For example, I was working while he called, Mei Mei was not sleeping when I was home, etc.
E) Present Perfect Progressive/Present Perfect Continuous - since, all the time, etc.
i) length of time of an action
ii) how long
For example, I have been studying Japanese since last year, I haven't had my lunch, etc.
F) Simple Past Perfect/Past Perfect Simple - already, just, never, etc.
i) past of present perfect
ii) already stopped
For example, I had been studying Japanese for two years before I moved to Japan, I hadn't taken my lunch yesterday, etc.
G) Future - will, going to.
* will - predictions, if, will do something, think that. For example, I will go soon, I think I won't go, etc.
* going to - already decided, is going to happen. For example, I am going to visit grandma tomorrow, Mei Mei is not going to school next week.
H) Future Progressive/Future Continuous - will be when.
i) an action will be continuous in the future
ii) something normally happens
For example, I will be working when you visit, he won't be going after work, etc.
I) Simple Future Perfect/Future Perfect Simple - will have,
i) something will happen (have happened before), will happen if.
For example, I will have taken my lunch if you are too late, Mei Mei wont have worked this coming Xmas, etc.
J) Future Perfect Progressive/Future Perfect Continuous - will have been.
i) how long it will be happening
For example, he will have been working for three years in November, I won't have been going to his house since the argument, etc.