for pooled and Panel:
I think u know "Panel data". But Pooled data is not a specialized definition.
for instance, u r doing a linear regression: regress consumption growth on expected income growth.
in your first estimation, you use US aggegate data.
in your 2nd effort, u could use Candian data.
on the other hand, for some reason, you may want to pool the Candian and US data together and do the regression.
to make thing clear, suppose you have 200 obs for US, and 199 obs for Canada,
then your sample size in your 1st regression is then 200, and 199 for your 2nd one.
in your 3rd, or pooled regression, the sample szie is 200+199.
now you are treating the pooled data as a sinsgle data set, and producing only one set of parameter estimations.