Formas de tiempos

Present Perfect
Function 1: Unspecified time
The Present Perfect verb tense can be used to express something in the past when we don't know when it happened or when it happened is not important.For example, "I've gained ten pounds!"
This function of this verb tense is often confusing for ESL students. Compare the Present Perfect usage to the Simple Past. "I traveled to Europe in 2004." TheSimple Past is used when a time is specified. The specified time could be "this morning," "yesterday," "at 6pm," "when I was a child," etc. "I've traveled to Europe." Since no time is specified, thePresent Perfect verb tense is used.
Function 2: Repetition
The Present Perfect is used to describe something that has happened many (or a couple of) times in the past. For example, "I've traveled toBrazil many times," "I've eaten at that restaurant twice," "John Grisham has written several books."
Function 3: Started in the past, continues until now, and may or may not continue into the futureFor example, "I've watched All My Children since 1970." This tense can often be replaced with the Present Perfect Progressive when emphasizing duration. "I've been watching soap operas since 1970."You'll notice that "for" and "since" are often clues to use the Present Perfect verb tense instead of the Simple Past.
Present Perfect Continuous
The Present Perfect Continuous has two functions:The first function; is to show the duration of an activity that began in the past and continues until the present time.
Here are some examples of this tense using this first function:
She has beenworking on this project for three years.
They have been acting strangely since they arrived.
The second function; is to talk about something that has been in progress recently or lately.
Here aresome examples of this tense using the second function:
You look great! Have you been working out lately?
I've been thinking about taking a trip to South America.

Simple Past Function
The Simple...