Let me answer to this question in English.
First of all, there is no stupid question in OHDSI.
‘Cohort’ table is a kind of ‘result’ table from the analysis, which is not usually generated during ETL process.
Usually, OHDSI ecosystem generates a cohort table for each analysis (or research project).
The cohort definition of OHDSI is: ‘A cohort is a set of persons who satisfy one or more inclusion criteria (a phenotype) for a duration of time’.
Subject_id of cohort is usually identical to the person_id of PERSON table. Cohort_definition_id represents unique identifier for the cohort. And cohort_start/end_date represents a duration of time for the cohort.
I hope this answer is helpful for you. @somacells