fact table and dimension table

Hi,

you can find complete informations here

https://docs.microsoft.com/en-us/power-bi/guidance/star-schema?source=docs

You can create a calculated column in any table

Hi AtchayaP ,

Fact Table:
It contains all the primary keys of the dimension and associated facts or measures(is a property on which calculations can be made) like count of items, total sales, average of sales etc.
Dimension Tables:
Dimension tables provides descriptive information for all the measurements recorded in fact table.
Dimensions are relatively very small in comparison of fact table.

A fact table holds the data to be analyzed, and a dimension table stores data about the ways in which the data in the fact table can be analyzed.

AtchayaP you can create columns in any table - Fact or Dim table. 
There are 2 schemas - Star Schema & Snowflakes Schema which require Fact & dimension tables. 

serpiva64 has mentioned a good link for understanding these schemas - https://docs.microsoft.com/en-us/power-bi/guidance/star-schema?source=docs .