In contrast to the BASIC form of verbs, the continuous form, also known as the progressive, is used to denote action that is progress, or that continues. That is, no definitive beginning and no definitive ending can be assigned in the continuous (progressive) forms.
Now, the Present Perfect Basic Form, an action that begins in the past and continues to the present moment at which it is used is an action that can be assigned a definitive time on each end--past and present. However, the present perfect continuous does not have any specific moment assigned to the two ends of time. That is, with the Present Perfect Continuous Form, the action that has begun in the past continues in the present as it is written or spoken about.
Sheryl has finished her assignment.[Having begun in the past, she now has completed the assignment]
Sheryle has been trying to finish her assignment for hours. [Having begun in the past, she is still working on it.]
Nevertheless, there is only a vague difference sometimes between Present Perfect Basic and Present Perfect Continuous because sometimes the action of the Present Perfect does continue to the present, rather than being completed in the present. For instance, there is little difference in the meanings of these two sentences.
We have lived in this town fifteen years. (We are still living here.)
We have been living here for fifteen years. (We are still living here.)
Strictly speaking, though, the word Perfect means completed, so the continuous form should really be used in the example's situation. But, Englsih speakers do often use the basic form.
The present perfect is used when the writer/speaker wants to convey that an action started in the past and continues to the present, or has just recently ended. To form the present perfect, use the PRESENT TENSE form of "to have" -- have/has + the past particple of the main verb. Here are a few examples:
The boys have practiced for the big show.
The team has cleaned up the mess on the field.
The instructor has taught all of the material needed for the test.
The present perfect continuous means the same thing, and is created by using the present tense of "to have" -- have/has + been + the "ing" form of the main verb. Here are a few examples:
You must have been shopping!
The rain has been coming down all day.
The children have been working hard on their projects.
The present perfect structure is used to talk about things that happened at some unspecified point in the past. There is no implication as to whether that action is continuing. For example, you could say "I have coached volleyball teams." This action occurred some time in the past and may or may not have continued.
The present perfect continuous is used to talk about things that started in the past and then continued until recently or are still happening. In this structure, we can say "I have been coaching volleyball teams since 2004." This implies that I am still doing so.