A table is best described as a structured set of data organised both horizontally (in rows) and vertically (in columns) providing an overview of information based on two (or exceptionally more) criteria. 
Generally, tables feature numerical data which is viewed from the point of view of two different values.
Tables are further divided into cells, ie single smallest structural units which tables are composed of.
We distinguish two types of tables, namely:

Example: Students' Attendance (featuring days of classes and competency levels)

Venue / Class         A2               B1                B2        
Monday        90 %             85 %       100 %
Tuesday        85 %      100 %       100 %
Wednesday        90 %       90 %       100 %
Thursday        60 %       70 %        90 %



For more information on tables, you may visit the following links:
1 Professional Tables
2 HTML Tables
3 IELTS Tables