Checkpoint is a verification point that compares a current
value for a specified property to a expected value for that
property.
In general for QTP we have six types of checkpoints they are:

1)Standard checkpoint:-Used to check the objects like Button
is enabled,disabled,focused etc

2)Text checkpoint:-Used to check for a text like the text in
the Label,etc

3)Bitmap checkpoint:-Used to compare the two bitmap images.

4)Database checkpoint:-Used to check for the database

5)Accessibility Chackpoint:-Used to check whether the
webpage satisfies their associated properties In QTP 9.1 to
see this gofor Tools->Options->Web->in that click on Advance
Button then u will find the properties with checkboxes.

6)XML Checkpoint:-Used to validate XML scripts

Checpoint is a verificatiion point that compare actual value
with the expected value during the run time.
QTP will have TEN types.
1. Standard Checkpoint
2. Text         "
3. Text Area     "
4. Bitmap
5. Database
6. Page          "
7. Image
8. Table 
9. Accessability
10. XML