Per Help (rephrased a little):
"...Field captions specify 1) the text for labels that will be attached to
controls created by dragging a field from the field list while designing
forms and 2) serves as the column heading for the field in either table or
query Datasheet view..."

The Caption property is Optional.  *IF* there is one, the Caption value will
appear in place of the field name as stated above. If there is no caption
the Field name will appear.

Why?
Examples: a lot of developers don't like spaces in field names, or they like
to preface the name with characters that tell them what type of field it is,
or use abbreviations in field names, etc.

Therefore, field names like:

EmployeeName
sngHourlyRate
SSN
fldNotes

Valid field names from a developer's point of view, but they are candidates
for "user friendly" captions like:

Employee Name
Hourly Rate
Social Security Number
Notes and Comments

The "user friendly" captions appear in place of the "developer friendly"
field names in the situations stated above.

Open the table in design view.
Select the field.
Look at the lower left of the screen.
If you type

This Is My Caption

in the Caption property of the field then you will see

This Is My Caption

as the caption of the field.

Insulting people who are trying to help you, and obviously asking to be
spoonfed answers so that you can avoid thinking or studying, is just going to
get you killfiled by the volunteers here. I'm of two minds whether to send
this... but be assured it's the first AND LAST time I'll spoon feed you.