Present Simple

Forming the positive is relatively easy. All you need to do is add an ‘s‘ to the verb when the subject is ‘he,’ ‘she,’ or ‘it.’ To make the negative form, you need to use ‘do not‘ (don’t) or ‘does not‘ (doesn’t). And we use ‘do‘ or ‘does‘ before the subject to make the ‘yes / no’ question.
Take the verb ‘work,’ for instance:

After he, she, and it, verbs in the present tense end in -s/-es
I work → he works
you play → she plays
we finish → it finishes

NOTE: When we add -s/-es to verbs there are sometimes changes in spelling.

play → plays (vowel + y, just add -s)
enjoy → enjoys (vowel + y, just add -s)

carry → carries (consonant + y,  remove the y and add -ies)
study → studies (consonant + y,  remove the y and add -ies)

wash → washes (verbs that end in s, sh, ch or x, add -es)
teach → teaches (verbs that end in s, sh, ch or x, add -es)

When to use the Present Simple:

We use the present simple to talk about repeated actions or habits. 

• I take a shower every morning. 
• Most evenings my parents stay at home and watch TV. 
• Do you go to the cinema very often? 
• What time does Kate finish work?

We use the present simple to talk about situations that are permanent (continuing for a long time). 

• Mr. and Mrs. Shaw live in NY. (That is their permanent home.) 
• He teaches English. (That is his job.)

We also use the present simple to talk about general truths. 

• The River Amazon flows into the Atlantic Ocean. 
• Vegetarians don’t eat meat or fish.

NOTE

• What do you do? is a question about someone’s occupation.
  ‘What do you do?’
  ‘I’m a doctor.’ 
• When who, what, or which is the subject of a present simple question, we do not use do/does.
  Who lives in that apartment?
• We often use words such as usually, often, every day with the present simple to say how often things happen.
  I usually take a shower every day.
• We also use the present simple to talk about the future.
  The train leaves at 7.30 tomorrow morning.