Grammar - Present Continuous / Progressive

The PRESENT PROGRESSIVE TENSE 

indicates continuing action, something going on now. This tense is formed with the helping "to be" verb, in the present tense, plus the present participle of the verb (with an -ing ending): "I am buying all my family's Christmas gifts early this year. She is working through the holiday break. Dierdre is being a really good girl in these days before Christmas".

The present progressive can suggest that an action is going to happen in the future, especially with verbs that convey the idea of a plan or of movement from one place or condition to another: "The team is arriving in two hours. He's moving to Portland this summer." Because the present progressive can suggest either the present or the future, it is usually modified by adverbs of time.

Generally, progressive forms occur only with what are called dynamic verbs and not with stative verbs.

Singular Plural
I am walking we are walking
you are walking you are walking
he/she/it is walking they are walking

Singular Plural
I am sleeping we are sleeping
you are sleeping you are sleeping
he/she/it is sleeping they are sleeping

Singular Plural
I am being we are being
you are being you are being
he/she/it is being they are being

For five generations, members of my family have been doctors.
Vaughan has batted clean-up since he came to the Redsox.
She has swum the English Channel every summer.
How long has it been since the last time we met?

http://grammar.ccc.commnet.edu/grammar/tenses/present_progressive.htm