Verb tenses: Present simple
Verbs come in three tenses: past, present, and future. The past is used to describe things that have already happened (e.g., earlier in the day, yesterday, last week, three years ago). The present tense is used to describe things that are happening right now, or things that are continuous. The future tense describes things that have yet to happen (e.g., later, tomorrow, next week, next year, three years from now).
Signal words
Simple Present
always, sometimes,
every day
\(1\). habits
\(2\). general truths
\(3\). repeated actions or 
\(4\). fixed arrangements 
    (present or future)
\(1\). He smokes.
\(2\). Water freezes at 
    zero degrees.
\(3\). We go to Tsaghkadzor 
     every winter.
\(4\). Your exams start at
Simple Past
last week,
(\(2\) days) ago
a completed action in the past (no connection to the present)
We saw a good film last week.
Simple Future
tomorrow, soon,
next year
promises and
I'll open the window.
I think he will help me.
Present Progressive (Continuous)
just now
right now
at the moment
\(1\). an action happening at
    the moment of speaking
\(2\). an action going on at a
    certain period of time
Look, they are playing football.
He’s studying a new language at the moment.
Past Progressive (Continuous)
all day long yesterday,
at this time yesterday,
at \(6\)
an action going on at a certain period of time in the past
I was riding my bike all day long yesterday.
I was watching TV at \(6\) o’clock yesterday.
I was eating breakfast at \(7:00\).
There is no future tense in time-clause and if-clause. 
After if and when we never use future tense. A present or past tense is used instead.
She will be glad if you go and see her.
We shall have dinner when father comes home.
Simple present tense verbs have a special form for the third person singular, they take the ending -s (works).