Present simple tense

The present simple (also called "simple present") tense mainly describes actions that happen frequently in the present time.
Forms.
Affirmative sentences.
In affirmative (or positive) sentences, the base verb is used. If the subject is 3rd person singular (she, he, it) an s, es or ies is added to the verb.
Negative sentences.
Negative sentences in the present simple are formed with do not or does not + base verb.
In informal situations and in speech, the short forms don't / doesn't may be used.
Questions.
Yes / No question are formed using Do / Does + subject + base verb.
Wh-questions begin with one of the wh-question words.
Uses of present simple tense.
General facts.
Statements of facts, which are always true, are expressed using the present simple tense.
Habits and routine actions.
Actions people frequently do, such as habits and routine actions, are expressed using the present simple tense.
Actions that are true for a long time.
These are actions that last for a long time like working or living in a certain place.
Scheduled events.
These events happen at scheduled times: classes, flight, bus trips, train trips,TV shows, etc.
With possible conditions.
The present simple verb is used in if conditionals (if clauses) types 0 and 1 to talk about possible conditions.
The verb to be.
The verb to be has 3 forms in the present simple.
The verb be is used to make affirmative and negative sentences and questions.
Adverbs of frequency.
Adverbs of frequency show how many times an action is repeated. The most common of these adverbs are: always, usually, often, sometimes, rarely, and never. Other expressions of frequency include the word every (every day, every week, etc.) and the adverbs "daily, weekly, etc".
Generally, adverbs of frequency come before the main verb of the sentence. However, if the main verb is a verb be, the adverb comes after the verb.