Market Capitalization is the total value of a company's stock.
Calculated as Number of outstanding shares x Closing share price for companies with a single type of share.
For multi class companies, Market cap is calculated as the sum of the number of outstanding shares x Closing share price for each class of shares.
The shares a company lists on the stock exchange are usually "ordinary shares". Sometimes companies issue other classes of share, such as preference shares, or Class A and Class B, which have different conditions attached. These types of share may or may not be listed. Infinancials includes all classes of share in its market cap, whether listed or not, to give an idea of the Entity Value of the company.

The current market capitalization is calculated using the last available share price.
The FYE market capitalization is calculated using the financial year end share price.
The 31/12 market capitalization is calculated using calendar year end share price.

The market capitalization does not necessarily reflect the actual value of a company, as is shown when a company launches a takeover bid for another and, as it frequently happens, pays a premium over the pre-bid price.