Present simple and continous.

We use present simple when we speak about permanent situations, facts, habits in the present, instructions, routines, opinions and time.

Structure:
-Affirmative: Subject + base form of the verb.
Example -- I speak Spanish.
- Negative: Subject + don’t/doesn’t + base form of the verb.
Example -- I don’t speak Spanish.
- Interrogative: Do/does + Subject + base form of the verb.
Example -- Do I speak Spanish?

We use present continous for actions that are happening at the moment, for arrangement in the future (I’m playing tennis tomorrow.), for temporary action or an action that annoys you.

Structure:
- Affirmative: Subject + am/is/are + verb finished in ING.
Example -- She is eating a sandwich.
- Negative: Subject + am not/isn’t/aren’t + verb finished in ING.
Example -- She isn’t eating a Sandwich.
- Interrogative: Am/is/are + subject + verb finished in ING + ?
Example -- Is she eating a sandwich?

There are some verbs that you can’t put them in a continous form, they are called State verbs…
They are verbs like… Be, Think, Love, Understand, Have, Like, Know, Smell, Touch, Taste…

Credits: http://web2.uvcs.uvic.ca/elc/studyzone/330/grammar/simcon1.htm