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Chapter 37: Progressive Tenses

Saying something like “I drink” is habitual… and is different from saying “I am drinking”.
-She “is doing” her homework.
-I “was standing” in line at the station.

This is achieved in Japanese by using the て form of the verb, directly attached to a form of います.

　　　pos　　　　　　　neg
pres ~ています　　　　~ていません
past ~ていました　　　~ていませんでした

so when using たべます, we can say:
ーたべています。　「I am eating.」
ーたべていません。　「I am not eating.」
ーたべていました。　「I was eating.」
ーたべていませんでした。　「I was not eating.」

います means “existence” so this is a pretty reasonable translation of “I am” and “I was”. “~て” is also very similar to “~ing” so the Japanese and English are very very similar in this sentence structure. (Rather Yoda-like actually, since we would literally be saying “Eating, I am”.

ーせんせいはよんでいました。　「Sensei was reading.」
ーそのひとはえきにたっていました。　「That person was standing at the station.」
ーいぬは、ねこをみていませんでした。　「The dog was not watching the cat.」
ーねこはねずみをみています。　「The cat is watching the mouse.」

This is often used in the present progressive (しっています) to mean “I know” (that you are already in the state of having learned). The second way it is used, is the ordinary present negative (しりません), to indicate that you are unaware of something.

ーしっています。　「I know.」
ーしりません。　「I don’t know.」
ーこのひとをしっていますか。　「Do you know this person?」
ーぞのひとをしりません。　「I don’t know that person.」

しっています is the plain, ordinary way of indicating that you already know what you are being told.
わかります used in the て form is a little more offhanded, and indicates the same thing.

ーしっています。　「I know.」
ーわかっています。　「I already know. (Gimme a break!)」

Note, that at this point it’s worth reviewing Chapter 21 (verbs), and Chapter 29 (verbs part 2) considering we’re at a point where we’re just using an additional way of expressing the verbs we’ve already learned.