The continuous (or progressive) tense comprises two parts: the verb "to be" in the present, past, or future tense, combined with the present participle of the main verb. It is a common verbal form in the English language, actually more common than the simple tense in the spoken language.
Let's find an example on Yabla English of the present continuous tense:
Time is running out.
Caption 29, George Clooney: Video diary from Sudan and Chad
To form the above present continuous tense, the present tense of the verb "to be" ("is") is combined with the present participle of the verb "to run" (by adding "ing," or in this case "-ning") to the end of the verb. The present continuous tense expresses something that is presently incomplete or unfinished. In the above case, there is still time enough now, but soon there will not be.
And the past continuous tense:
I was laughing so hard.
Caption 42, Jim White: Interview
To form the above past continuous tense, the past tense of the verb "to be" ("was") is combined with the present participle of the verb "to laugh." The past continuous tense expresses something that is incomplete or unfinished in the past. In the above case, laughing was occurring during a past event.
And lastly, the future continuous tense:
This is where you will be working from.
Caption 14, Business English: Starting on a new job
To form the above future continuous tense, the future tense of the verb "to be" ("will be") is combined with the present participle of the verb "to work." The future continuous tense expresses something is incomplete or unfinished that will happen in the future. In the above case, work will be performed at some point in the future.
Take a look at this list of basic verb forms, and search Yabla English for some of your favorite English present participle verbs (ending in -ing) and see these tenses used in a real-world context.