what are uri, contentValues

Question

Can anyone explain me about each term that I have used in working with calendar events?

1. Uri event_uri = Uri.parse("content://com.android.calendar/" + "events");
   What is uri here, what actually is content, as we can initialize int value to 0? Is it
   possible to initialize a uri with a default value?

2. Uri reminder_uri = Uri.parse("content://com.android.calendar/" + "reminders");
   What signifies these uri? What are the differences between event_uri and reminder_uri?

3. ContentValues values = new ContentValues();
values.put("calendar_id", 1);
values.put("title", str);
values.put("description", m_strDescription);
   What does the first one do? values.put("calendar_id", 1);

4. ContentResolver cr = getContentResolver();
   What is the use of the content resolver? Sometimes we write:

   Uri u = cr.insert(event_uri, values)
   What is this uri? How does it differ from the first two uris e.g event_uri and reminder_uri

   Again values.put("event_id", Long.parseLong(event.getLastPathSegment())); cr.insert(remindar_uri, values);

   What does it do?